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1.
Plant Cell Environ ; 46(8): 2470-2491, 2023 08.
Article in English | MEDLINE | ID: mdl-37222394

ABSTRACT

In response to Ca2+ signals, the evolutionarily-conserved Ca2+ sensor calmodulin (CaM) regulates protein targets via direct interaction. Plants possess many CaM-like (CML) proteins, but their binding partners and functions are mostly unknown. Here, using Arabidopsis CML13 as 'bait' in a yeast two-hybrid screen, we isolated putative targets from three, unrelated protein families, namely, IQD proteins, calmodulin-binding transcriptional activators (CAMTAs) and myosins, all of which possess tandem isoleucine-glutamine (IQ) structural domains. Using the split-luciferase complementation assay in planta and the yeast 2-hybrid system, CML13 and CML14 showed a preference for interaction with tandem over single IQ domains. Relative to CaM, CML13 and CML14 displayed weaker signals when tested with the non-IQ, CaM-binding domain of glutamate decarboxylase or the single IQ domains of CNGC20 (cyclic-nucleotide gated channel-20) or IQM1 (IQ motif protein1). We examined IQD14 as a representative tandem IQ-protein and found that only CaM, CML13 and CML14 interacted with IQD14 among 12 CaM/CMLs tested. CaM, CML13 and CML14 bound in vitro to IQD14 in the presence or absence of Ca2+ . Binding affinities were in the nM range and were higher when two tandem IQ domains from IQD14 were present. Green fluorescent protein-tagged versions of CaM, CML13 and CML14 localized to both the cytosol and nucleus in plant cells but were partially relocalized to the microtubules when co-expressed with IQD14 tagged with mCherry. These and other data are discussed in the context of possible roles for these CMLs in gene regulation via CAMTAs and cytoskeletal activity via myosins and IQD proteins.


Subject(s)
Arabidopsis Proteins , Arabidopsis , Arabidopsis/genetics , Arabidopsis/metabolism , Calmodulin/genetics , Calmodulin/metabolism , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Saccharomyces cerevisiae/metabolism , Calcium Signaling , Protein Binding , Calcium/metabolism
2.
Protein Sci ; 32(7): e4685, 2023 07.
Article in English | MEDLINE | ID: mdl-37222490

ABSTRACT

Cyanophycin is a natural polymer composed of a poly-aspartate backbone with arginine attached to each of the aspartate sidechains. Produced by a wide range of bacteria, which mainly use it as a store of fixed nitrogen, it has many promising industrial applications. Cyanophycin can be synthesized from the amino acids Asp and Arg by the widespread cyanophycin synthetase 1 (CphA1), or from the dipeptide ß-Asp-Arg by the cyanobacterial enzyme cyanophycin synthetase 2 (CphA2). CphA2 enzymes display a range of oligomeric states, from dimers to dodecamers. Recently, the crystal structure of a CphA2 dimer was solved but could not be obtained in complex with substrate. Here, we report cryo-EM structures of the hexameric CphA2 from Stanieria sp. at ~2.8 Å resolution, both with and without ATP analog and cyanophycin. The structures show a two-fold symmetrical, trimer-of-dimers hexameric architecture, and substrate-binding interactions that are similar to those of CphA1. Mutagenesis experiments demonstrate the importance of several conserved substrate-binding residues. We also find that a Q416A/R528G double mutation prevents hexamer formation and use this double mutant to show that hexamerization augments the rate of cyanophycin synthesis. Together, these results increase our mechanistic understanding of how an interesting green polymer is biosynthesized.


Subject(s)
Cyanobacteria , Peptide Synthases , Peptide Synthases/chemistry , Aspartic Acid , Bacterial Proteins/chemistry
3.
PLoS Pathog ; 17(10): e1009965, 2021 10.
Article in English | MEDLINE | ID: mdl-34637487

ABSTRACT

Mycobacterium abscessus is the most common rapidly growing non-tuberculous mycobacteria to cause pulmonary disease in patients with impaired lung function such as cystic fibrosis. M. abscessus displays high intrinsic resistance to common antibiotics and inducible resistance to macrolides like clarithromycin. As such, M. abscessus is clinically resistant to the entire regimen of front-line M. tuberculosis drugs, and treatment with antibiotics that do inhibit M. abscessus in the lab results in cure rates of 50% or less. Here, we identified epetraborole (EPT) from the MMV pandemic response box as an inhibitor against the essential protein leucyl-tRNA synthetase (LeuRS) in M. abscessus. EPT protected zebrafish from lethal M. abscessus infection and did not induce self-resistance nor against clarithromycin. Contrary to most antimycobacterials, the whole-cell activity of EPT was greater against M. abscessus than M. tuberculosis, but crystallographic and equilibrium binding data showed that EPT binds LeuRSMabs and LeuRSMtb with similar residues and dissociation constants. Since EPT-resistant M. abscessus mutants lost LeuRS editing activity, these mutants became susceptible to misaminoacylation with leucine mimics like the non-proteinogenic amino acid norvaline. Proteomic analysis revealed that when M. abscessus LeuRS mutants were fed norvaline, leucine residues in proteins were replaced by norvaline, inducing the unfolded protein response with temporal changes in expression of GroEL chaperonins and Clp proteases. This supports our in vitro data that supplementation of media with norvaline reduced the emergence of EPT mutants in both M. abscessus and M. tuberculosis. Furthermore, the combination of EPT and norvaline had improved in vivo efficacy compared to EPT in a murine model of M. abscessus infection. Our results emphasize the effectiveness of EPT against the clinically relevant cystic fibrosis pathogen M. abscessus, and these findings also suggest norvaline adjunct therapy with EPT could be beneficial for M. abscessus and other mycobacterial infections like tuberculosis.


Subject(s)
Antitubercular Agents/pharmacology , Mycobacterium Infections, Nontuberculous , Mycobacterium abscessus/drug effects , Valine/analogs & derivatives , Animals , Drug Therapy, Combination/methods , Mice , Mice, Inbred NOD , Mice, SCID , Valine/pharmacology , Zebrafish
4.
J Biol Chem ; 295(13): 4303-4315, 2020 03 27.
Article in English | MEDLINE | ID: mdl-32098872

ABSTRACT

The E-protein transcription factors guide immune cell differentiation, with E12 and E47 (hereafter called E2A) being essential for B-cell specification and maturation. E2A and the oncogenic chimera E2A-PBX1 contain three transactivation domains (ADs), with AD1 and AD2 having redundant, independent, and cooperative functions in a cell-dependent manner. AD1 and AD2 both mediate their functions by binding to the KIX domain of the histone acetyltransferase paralogues CREB-binding protein (CBP) and E1A-binding protein P300 (p300). This interaction is necessary for B-cell maturation and oncogenesis by E2A-PBX1 and occurs through conserved ΦXXΦΦ motifs (with Φ denoting a hydrophobic amino acid) in AD1 and AD2. However, disruption of this interaction via mutation of the KIX domain in CBP/p300 does not completely abrogate binding of E2A and E2A-PBX1. Here, we determined that E2A-AD1 and E2A-AD2 also interact with the TAZ2 domain of CBP/p300. Characterization of the TAZ2:E2A-AD1(1-37) complex indicated that E2A-AD1 adopts an α-helical structure and uses its ΦXXΦΦ motif to bind TAZ2. Whereas this region overlapped with the KIX recognition region, key KIX-interacting E2A-AD1 residues were exposed, suggesting that E2A-AD1 could simultaneously bind both the KIX and TAZ2 domains. However, we did not detect a ternary complex involving E2A-AD1, KIX, and TAZ2 and found that E2A containing both intact AD1 and AD2 is required to bind to CBP/p300. Our findings highlight the structural plasticity and promiscuity of E2A-AD1 and suggest that E2A binds both the TAZ2 and KIX domains of CBP/p300 through AD1 and AD2.


Subject(s)
CREB-Binding Protein/chemistry , E1A-Associated p300 Protein/genetics , Protein Domains/genetics , Transcription Factor 3/chemistry , B-Lymphocytes/chemistry , B-Lymphocytes/metabolism , CREB-Binding Protein/genetics , CREB-Binding Protein/ultrastructure , E1A-Associated p300 Protein/chemistry , E1A-Associated p300 Protein/ultrastructure , Homeodomain Proteins/chemistry , Homeodomain Proteins/genetics , Homeodomain Proteins/ultrastructure , Humans , Mutation/genetics , Oncogene Proteins, Fusion/chemistry , Oncogene Proteins, Fusion/genetics , Oncogene Proteins, Fusion/ultrastructure , Protein Binding/genetics , Protein Conformation , Transcription Factor 3/genetics , Transcription Factor 3/ultrastructure
5.
Age Ageing ; 49(3): 432-438, 2020 04 27.
Article in English | MEDLINE | ID: mdl-31971573

ABSTRACT

BACKGROUND: Although there is evidence of suboptimal outcomes in older people with chronic pain, little emphasis has been placed on those in remote and rural settings. OBJECTIVE: To describe the perspectives of older people in the Scottish Highlands on their chronic pain management. DESIGN: Cross-sectional survey. SETTING: NHS Highland, the most remote and rural geographical health board in Scotland. SUBJECTS: Home-dwelling members of the public aged ≥70 years. METHODS: Anonymised questionnaires were mailed to a random sample of 1800 older people. Questionnaire items were demographics, nature of any chronic pain, management regimens and perceived effectiveness. Validated scales were the Pain Disability Questionnaire and the Tampa Scale for Kinesiophobia. RESULTS: Adjusted response rate was 39.3% (709/1755). One-quarter (25.0%, n = 177) were experiencing chronic pain, being more likely to live in deprived areas (P < 0.05). Median pain intensity was 6 (IQR 4-7, 10 high), causing distress (median 5, IQR 3-7). Respondents largely consulted GPs (66.1%, n = 117) with a minority (16.4%, n = 29) referred to a specialist pain clinic and few consulting other health professionals. Over three quarters (78.0%, n = 138) were receiving prescribed medicines, most commonly paracetamol, alone (35.6%, n = 63) or in combination with opioids (16.4%, n = 29). One-third (31.6%, n = 56) expressed a desire for more effective medicines; few reported using any non-pharmacological therapies. The median scores for the Pain Disability Questionnaire and Tampa Scale for Kinesiophobia were 74 (IQR 34-104.5, 150 high) and 40 (IQR 35-45, 68 high). CONCLUSIONS: Evidence of provision of appropriate integrated and person-centred chronic pain care is lacking.


Subject(s)
Chronic Pain , Aged , Chronic Pain/diagnosis , Chronic Pain/drug therapy , Chronic Pain/epidemiology , Cross-Sectional Studies , Humans , Rural Population , Scotland/epidemiology , Surveys and Questionnaires
6.
J Mol Biol ; 431(7): 1370-1379, 2019 03 29.
Article in English | MEDLINE | ID: mdl-30826376

ABSTRACT

The proliferating cell nuclear antigen (PCNA) is a sliding clamp associated with DNA polymerases and serves as a binding platform for the recruitment of regulatory proteins linked to DNA damage repair, cell cycle regulation, and epigenetic signaling. The histone H3 lysine-27 (H3K27) mono-methyltransferase Arabidopsis trithorax-related protein 5/6 (ATXR5/6) associates with PCNA, and this interaction has been proposed to act as a key determinant controlling the reestablishment of H3K27 mono-methylation following replication. In this study, we provide biochemical evidence showing that PCNA inhibits ATXR6 enzymatic activity. The structure of the ATXR6 PCNA-interacting peptide (PIP) in complex with PCNA indicates that a trio of hydrophobic residues contributes to the binding of the enzyme to the sliding clamp. Finally, despite the presence of three PIP binding clefts, only two molecules of ATXR6 bind to PCNA likely enabling the recruitment of a third protein to the sliding clamp. Collectively, these results rule out the model wherein PCNA-bound ATXR6 actively reestablishes H3K27 mono-methylation following DNA replication and provides insights into the role of ATXR6 PIP motif in its interaction with PCNA.


Subject(s)
Arabidopsis Proteins/metabolism , Methyltransferases/metabolism , Nucleosomes/metabolism , Proliferating Cell Nuclear Antigen/metabolism , Protein Interaction Domains and Motifs , Arabidopsis/metabolism , Arabidopsis Proteins/chemistry , Arabidopsis Proteins/genetics , DNA Replication , Gene Expression Regulation, Plant , Histones/metabolism , Methylation , Methyltransferases/chemistry , Methyltransferases/genetics , Models, Molecular , Proliferating Cell Nuclear Antigen/chemistry , Proliferating Cell Nuclear Antigen/genetics , Protein Binding , Protein Conformation , Sequence Analysis, Protein
7.
ACS Appl Mater Interfaces ; 10(21): 17560-17570, 2018 May 30.
Article in English | MEDLINE | ID: mdl-29741868

ABSTRACT

Sensor surfaces play a predominant role in the development of optical biosensor technologies for the analysis of biomolecular interactions. Thiol-based self-assembled monolayers (SAMs) on gold have been widely used as linker layers for sensor surfaces. However, the degradation of the thiol-gold bond can limit the performance and durability of such surfaces, directly impacting their performance and cost-effectiveness. To this end, a new family of materials based on N-heterocyclic carbenes (NHCs) has emerged as an alternative for surface modification, capable of self-assembling onto a gold surface with higher affinity and superior stability as compared to the thiol-based systems. Here we demonstrate three applications of NHC SAMs supporting a dextran layer as a tunable platform for developing various affinity-capture biosensor surfaces. We describe the development and testing of NHC-based dextran biosensor surfaces modified with each of streptavidin, nitrilotriacetic acid, and recombinant Protein A. These affinity-capture sensor surfaces enable oriented binding of ligands for optimal performance in biomolecular assays. Together, the intrinsic high stability and flexible design of the NHC biosensing platforms show great promise and open up exciting possibilities for future biosensing applications.


Subject(s)
Biosensing Techniques , Dextrans , Gold , Methane/analogs & derivatives
8.
Langmuir ; 33(49): 13936-13944, 2017 12 12.
Article in English | MEDLINE | ID: mdl-29141140

ABSTRACT

Surface plasmon resonance (SPR)-based biosensing is a powerful tool to study the recognition processes between biomolecules in real-time without need for labels. The use of thiol chemistry is a critical component in surface functionalization of various SPR biosensor surfaces on gold. However, its use is hampered by the high propensity for oxidation of the gold-thiol linkage even in ambient atmosphere, resulting in a short lifetime of SPR sensor chips unless strict precautions are taken. Herein, we describe an approach to overcome this limitation by employing highly robust self-assembled monolayers (SAMs) of alkylated N-heterocyclic carbenes (NHCs) on gold. An alkylated NHC sensor surface was developed and its biosensing capabilities were compared to a commercial thiol-based analogue-a hydrophobic association (HPA) chip-in terms of its ability to act as a reliable platform for biospecific interaction analysis under a wide range of conditions. The NHC-based SPR sensor outperforms related thiol-based sesnsors in several aspects, including lower nonspecific binding capacity, better chemical stability, higher reproducibility, shorter equilibration time, and longer life span. We also demonstrate that the NHC-based sensor can be used for rapid and efficient formation of a hybrid lipid bilayer for use in membrane interaction studies. Overall, this work identifies the great promise in designing NHC-based surfaces as a new technology platform for SPR-based biosensing.


Subject(s)
Methane/analogs & derivatives , Biosensing Techniques , Gold , Methane/chemistry , Reproducibility of Results , Surface Plasmon Resonance
9.
ACS Appl Mater Interfaces ; 9(45): 39223-39234, 2017 Nov 15.
Article in English | MEDLINE | ID: mdl-29048150

ABSTRACT

Surface chemistry is a key enabler for various biosensing applications. Biosensors based on surface plasmon resonance routinely employ thiol-based chemistry for the linker layer between gold-coated support surfaces and functional biosensor surfaces. However, there is a growing awareness that such sensor surfaces are prone to oxidation/degradation problems in the presence of oxygen, and previous efforts to improve the stability have shown limited advancements. As an alternative, recent studies employing N-heterocyclic carbene (NHC) self-assembled monolayers (SAMs) deposited on gold have shown significant promise in this area. Here, we describe a sensor surface employing an NHC SAM to couple a modified carboxymethylated dextran onto a gold surface. Such a dextran matrix is also used for affinity chromatography, and it is the most commonly employed matrix for commercial biosensor surfaces today. The performance reliability of the dextran-modified NHC chip to act as an alternative biosensing platform is compared with that of a thiol-based commercial chip in the proof-of-concept tests. The resultant NHC sensor surface shows a higher thermal stability compared to thiol analogues. Moreover, the plasma protein/drug and antibody/antigen interactions were validated on the NHC-based dextran chip and showed similar performance as compared to the thiol-based commercial chip. Ultimately, this study shows the strong potential applicability of chemical modifications to gold surfaces using NHC ligands for biosensing applications.


Subject(s)
Dextrans/chemistry , Biosensing Techniques , Gold , Methane/analogs & derivatives , Reproducibility of Results , Surface Plasmon Resonance
10.
Front Plant Sci ; 8: 2175, 2017.
Article in English | MEDLINE | ID: mdl-29312414

ABSTRACT

Calcium ions are used as ubiquitous, key second messengers in cells across eukaryotic taxa. In plants, calcium signal transduction is involved in a wide range of cellular processes from abiotic and biotic stress responses to development and growth. Calcium signals are detected by calcium sensor proteins, of which calmodulin (CaM), is the most evolutionarily conserved and well-studied. These sensors regulate downstream targets to propagate the information in signaling pathways. Plants possess a large family of calcium sensors related to CaM, termed CaM-like (CMLs), that are not found in animals and remain largely unstudied at the structural and functional level. Here, we investigated the biochemical properties and gene promoter activity of two closely related members of the Arabidopsis CML family, CML15 and CML16. Biochemical characterization of recombinant CML15 and CML16 indicated that they possess properties consistent with their predicted roles as calcium sensors. In the absence of calcium, CML15 and CML16 display greater intrinsic hydrophobicity than CaM. Both CMLs displayed calcium-dependent and magnesium-independent conformational changes that expose hydrophobic residues, but the degree of hydrophobic exposure was markedly less than that observed for CaM. Isothermal titration calorimetry indicated two and three calcium-binding sites for CML15 and CML16, respectively, with affinities expected to be within a physiological range. Both CML15 and CML16 bound calcium with high affinity in the presence of excess magnesium. Promoter-reporter analysis demonstrated that the CML16 promoter is active across a range of Arabidopsis tissues and developmental stages, whereas the CML15 promoter activity is very restricted and was observed only in floral tissues, specifically anthers and pollen. Collectively, our data indicate that these CMLs behave biochemically like calcium sensors but with properties distinct from CaM and likely have non-overlapping roles in floral development. We discuss our findings in the broader context of calcium sensors and signaling in Arabidopsis.

11.
Nat Commun ; 7: 12654, 2016 09 02.
Article in English | MEDLINE | ID: mdl-27585494

ABSTRACT

The formation of organic films on gold employing N-heterocyclic carbenes (NHCs) has been previously shown to be a useful strategy for generating stable organic films. However, NHCs or NHC precursors typically require inert atmosphere and harsh conditions for their generation and use. Herein we describe the use of benzimidazolium hydrogen carbonates as bench stable solid precursors for the preparation of NHC films in solution or by vapour-phase deposition from the solid state. The ability to prepare these films by vapour-phase deposition permitted the analysis of the films by a variety of surface science techniques, resulting in the first measurement of NHC desorption energy (158±10 kJ mol(-1)) and confirmation that the NHC sits upright on the surface. The use of these films in surface plasmon resonance-type biosensing is described, where they provide specific advantages versus traditional thiol-based films.

12.
Plant Cell ; 28(7): 1738-51, 2016 07.
Article in English | MEDLINE | ID: mdl-27335451

ABSTRACT

Ca(2+) signaling is critical to plant immunity; however, the channels involved are poorly characterized. Cyclic nucleotide-gated channels (CNGCs) are nonspecific, Ca(2+)-permeable cation channels. Plant CNGCs are hypothesized to be negatively regulated by the Ca(2+) sensor calmodulin (CaM), and previous work has focused on a C-terminal CaM-binding domain (CaMBD) overlapping with the cyclic nucleotide binding domain of plant CNGCs. However, we show that the Arabidopsis thaliana isoform CNGC12 possesses multiple CaMBDs at cytosolic N and C termini, which is reminiscent of animal CNGCs and unlike any plant channel studied to date. Biophysical characterizations of these sites suggest that apoCaM interacts with a conserved isoleucine-glutamine (IQ) motif in the C terminus of the channel, while Ca(2+)/CaM binds additional N- and C-terminal motifs with different affinities. Expression of CNGC12 with a nonfunctional N-terminal CaMBD constitutively induced programmed cell death, providing in planta evidence of allosteric CNGC regulation by CaM. Furthermore, we determined that CaM binding to the IQ motif was required for channel function, indicating that CaM can both positively and negatively regulate CNGC12. These data indicate a complex mode of plant CNGC regulation by CaM, in contrast to the previously proposed competitive ligand model, and suggest exciting parallels between plant and animal channels.


Subject(s)
Arabidopsis Proteins/metabolism , Arabidopsis/metabolism , Calmodulin/metabolism , Cyclic Nucleotide-Gated Cation Channels/metabolism , Arabidopsis/genetics , Arabidopsis Proteins/genetics , Binding Sites , Calcium/metabolism , Calmodulin/genetics , Cyclic Nucleotide-Gated Cation Channels/genetics , Plant Immunity/genetics , Plant Immunity/physiology , Protein Binding/genetics , Protein Binding/physiology , Signal Transduction/genetics , Signal Transduction/physiology
13.
J Biol Chem ; 289(24): 17030-42, 2014 Jun 13.
Article in English | MEDLINE | ID: mdl-24790102

ABSTRACT

Dictyostelium discoideum MyoB is a class I myosin involved in the formation and retraction of membrane projections, cortical tension generation, membrane recycling, and phagosome maturation. The MyoB-specific, single-lobe EF-hand light chain MlcB binds the sole IQ motif of MyoB with submicromolar affinity in the absence and presence of Ca(2+). However, the structural features of this novel myosin light chain and its interaction with its cognate IQ motif remain uncharacterized. Here, we describe the NMR-derived solution structure of apoMlcB, which displays a globular four-helix bundle. Helix 1 adopts a unique orientation when compared with the apo states of the EF-hand calcium-binding proteins calmodulin, S100B, and calbindin D9k. NMR-based chemical shift perturbation mapping identified a hydrophobic MyoB IQ binding surface that involves amino acid residues in helices I and IV and the functional N-terminal Ca(2+) binding loop, a site that appears to be maintained when MlcB adopts the holo state. Complementary mutagenesis and binding studies indicated that residues Ile-701, Phe-705, and Trp-708 of the MyoB IQ motif are critical for recognition of MlcB, which together allowed the generation of a structural model of the apoMlcB-MyoB IQ complex. We conclude that the mode of IQ motif recognition by the novel single-lobe MlcB differs considerably from that of stereotypical bilobal light chains such as calmodulin.


Subject(s)
Dictyostelium/metabolism , Myosin Light Chains/chemistry , Nonmuscle Myosin Type IIB/chemistry , Protozoan Proteins/chemistry , Amino Acid Sequence , Binding Sites , Calcium/metabolism , Dictyostelium/chemistry , EF Hand Motifs , Molecular Sequence Data , Mutation , Myosin Light Chains/genetics , Myosin Light Chains/metabolism , Nonmuscle Myosin Type IIB/genetics , Nonmuscle Myosin Type IIB/metabolism , Protein Binding , Protozoan Proteins/metabolism
14.
Nucleic Acids Res ; 42(11): 7370-82, 2014 Jun.
Article in English | MEDLINE | ID: mdl-24682819

ABSTRACT

The E-protein transcription factors play essential roles in lymphopoiesis, with E12 and E47 (hereafter called E2A) being particularly important in B cell specification and maturation. The E2A gene is also involved in a chromosomal translocation that results in the leukemogenic oncoprotein E2A-PBX1. The two activation domains of E2A, AD1 and AD2, display redundant, independent, and cooperative functions in a cell-dependent manner. AD1 of E2A functions by binding the transcriptional co-activator CBP/p300; this interaction is required in oncogenesis and occurs between the conserved ϕ-x-x-ϕ-ϕ motif in AD1 and the KIX domain of CBP/p300. However, co-activator recruitment by AD2 has not been characterized. Here, we demonstrate that the first of two conserved ϕ-x-x-ϕ-ϕ motifs within AD2 of E2A interacts at the same binding site on KIX as AD1. Mutagenesis uncovered a correspondence between the KIX-binding affinity of AD2 and transcriptional activation. Although AD2 is dispensable for oncogenesis, experimentally increasing the affinity of AD2 for KIX uncovered a latent potential to mediate immortalization of primary hematopoietic progenitors by E2A-PBX1. Our findings suggest that redundancy between the two E2A activation domains with respect to transcriptional activation and oncogenic function is mediated by binding to the same surface of the KIX domain of CBP/p300.


Subject(s)
Transcription Factor 3/chemistry , Transcriptional Activation , p300-CBP Transcription Factors/chemistry , Binding Sites , Bone Marrow Cells/metabolism , Models, Molecular , Protein Interaction Domains and Motifs , Protein Structure, Tertiary , Transcription Factor 3/metabolism , p300-CBP Transcription Factors/metabolism
15.
Biochem J ; 457(1): 127-36, 2014 Jan 01.
Article in English | MEDLINE | ID: mdl-24102643

ABSTRACT

Many signalling pathways in plants are regulated by the second messenger calcium (Ca(2+)). In the standard model, Ca(2+)-sensor proteins, such as CaM (calmodulin), detect Ca(2+) signals and subsequently regulate downstream targets to advance the signal transduction cascade. In addition to CaM, plants possess many CMLs (CaM-like proteins) that are predicted to function as Ca(2+) sensors, but which remain largely uncharacterized. In the present study, we examined the biochemical properties, subcellular localization and tissue-specific distribution of Arabidopsis CML43. Our data indicate that CML43 displays characteristics typical of Ca(2+) sensors, including high-affinity Ca(2+) binding, conformational changes upon Ca(2+) binding that expose hydrophobic regions and stabilization of structure in the presence of Mg(2+) or Ca(2+). In vivo localization analysis demonstrates that CML43 resides in cytosolic and nuclear compartments. Transgenic plants expressing a CML43:GUS (ß-glucoronidase) promoter reporter gene revealed that CML43 promoter activity is restricted almost exclusively to root tips under normal growth conditions. GUS reporter activity in these transgenic plants was strongly increased when exposed to the defence compound SA (salicylic acid). Furthermore, immunoblot analysis revealed that the CML43 protein accumulates following treatment with SA. Collectively, our findings suggest that CML43 functions as a Ca(2+) sensor in root tips during both normal growth and plant immune response.


Subject(s)
Arabidopsis Proteins/physiology , Arabidopsis , Calcium-Binding Proteins/physiology , Calcium/metabolism , Gene Expression Regulation, Plant/drug effects , Salicylic Acid/pharmacology , Arabidopsis/drug effects , Arabidopsis/physiology , Calcium-Binding Proteins/chemistry , Calmodulin/genetics , Cells, Cultured , Immune System/metabolism , Organ Specificity/drug effects , Organ Specificity/genetics , Plant Roots/drug effects , Plant Roots/genetics , Plant Roots/metabolism , Plants, Genetically Modified , Sequence Homology , Signal Transduction/drug effects , Signal Transduction/genetics , Nicotiana
16.
Cell Signal ; 24(9): 1790-6, 2012 Sep.
Article in English | MEDLINE | ID: mdl-22588125

ABSTRACT

Calmodulin (CaM), a ubiquitous calcium-binding protein, regulates numerous cellular processes, primarily in response to calcium flux. We have identified and characterized a novel interaction between CaM and ß-p21-activated kinase interacting exchange factor (ß-PIX), a putative guanine exchange factor implicated in cell signaling, using affinity pull-down assays, co-immunoprecipitation, co-localization and circular dichroism studies. Fluorescence-based titration and isothermal titration calorimetry experiments revealed a Ca(2+)-dependent binding mechanism (K(D)≤10µM). Further, we show that CaM participates in a multi-protein complex involving ß-PIX and E3 ubiquitin ligase c-Cbl (casitas B-cell lymphoma), which may play a critical role in receptor tyrosine kinase regulation and downstream signaling.


Subject(s)
Calmodulin/metabolism , Receptor Protein-Tyrosine Kinases/metabolism , Rho Guanine Nucleotide Exchange Factors/metabolism , Calcium/metabolism , Calmodulin/chemistry , Cell Line, Tumor , Humans , Rho Guanine Nucleotide Exchange Factors/chemistry
17.
PLoS One ; 7(4): e34680, 2012.
Article in English | MEDLINE | ID: mdl-22496840

ABSTRACT

The C/EBP Homologous Protein (CHOP) is a nuclear protein that is integral to the unfolded protein response culminating from endoplasmic reticulum stress. Previously, CHOP was shown to comprise extensive disordered regions and to self-associate in solution. In the current study, the intrinsically disordered nature of this protein was characterized further by comprehensive in silico analyses. Using circular dichroism, differential scanning calorimetry and nuclear magnetic resonance, we investigated the global conformation and secondary structure of CHOP and demonstrated, for the first time, that conformational changes in this protein can be induced by the free amino acid L-cysteine. Addition of L-cysteine caused a significant dose-dependent decrease in the protein helicity--dropping from 69.1% to 23.8% in the presence of 1 mM of L-cysteine--and a sequential transition to a more disordered state, unlike that caused by thermal denaturation. Furthermore, the presence of small amounts of free amino acid (80 µM, an 8:1 cysteine∶CHOP ratio) during CHOP thermal denaturation altered the molecular mechanism of its melting process, leading to a complex, multi-step transition. On the other hand, high levels (4 mM) of free L-cysteine seemed to cause a complete loss of rigid cooperatively melting structure. These results suggested a potential regulatory function of L-cysteine which may lead to changes in global conformation of CHOP in response to the cellular redox state and/or endoplasmic reticulum stress.


Subject(s)
Cysteine/chemistry , Transcription Factor CHOP/chemistry , Circular Dichroism , Cysteine/pharmacology , Endoplasmic Reticulum Stress , Humans , Oxidation-Reduction , Protein Conformation , Protein Denaturation/drug effects
18.
Br J Clin Pharmacol ; 73(4): 656-60, 2012 Apr.
Article in English | MEDLINE | ID: mdl-22035442

ABSTRACT

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT: Pharmacists, along with certain other health professionals, may train and practice as supplementary or independent prescribers. The implementation and sustainability of pharmacist prescribing services throughout Britain will require a sizeable workforce. However, a survey of GB pharmacists highlighted that only a minority has taken any action to investigate prescribing training. Newly registered pharmacists may be keen to explore extended clinical roles and their engagement is likely to be key to the future success of this initiative. WHAT THIS STUDY ADDS: Newly registered pharmacists are cautious in their approach to taking on prescribing training and roles. While almost all expressed interest in prescribing training, they acknowledged training needs in clinical examination, patient monitoring and medico-legal aspects of prescribing. Longitudinal research on a cohort of newly registered pharmacist prescribers is warranted, aiming to identify later prescribing training actions and subsequent impact on patient care. AIM To investigate newly registered pharmacists' awareness of pharmacist prescribing and views on potential future roles as prescribers. METHODS: A mailed questionnaire was sent to all 1658 pharmacists joining the Pharmacist Register in 2009. RESULTS: The response rate was 25.2% (n= 418). While most (86.4%) expressed interest in prescribing training, they acknowledged training needs in clinical examination, patient monitoring and medico-legal aspects of prescribing. Two thirds of respondents (66.3%) thought the current requirement of being registered as a pharmacist for 2 years prior to commencing prescribing training was appropriate. CONCLUSION: Newly registered pharmacists are cautious in their approach to taking on prescribing training and roles.


Subject(s)
Attitude of Health Personnel , Drug Prescriptions , Pharmacists/psychology , Cross-Sectional Studies , Education, Pharmacy , Education, Pharmacy, Continuing , Female , Humans , Male , Professional Competence , Professional Role/psychology , Surveys and Questionnaires , United Kingdom
19.
Cell Host Microbe ; 10(2): 158-64, 2011 Aug 18.
Article in English | MEDLINE | ID: mdl-21843872

ABSTRACT

By sequestering manganese and zinc, the neutrophil protein calprotectin plays a crucial role in host defense against bacterial and fungal pathogens. However, the essential processes disrupted by calprotectin remain unknown. We report that calprotectin enhances the sensitivity of Staphylococcus aureus to superoxide through inhibition of manganese-dependent bacterial superoxide defenses, thereby increasing superoxide levels within the bacterial cell. Superoxide dismutase activity is required for full virulence in a systemic model of S. aureus infection, and disruption of staphylococcal superoxide defenses by calprotectin augments the antimicrobial activity of neutrophils promoting in vivo clearance. Calprotectin mutated in two transition metal binding sites and therefore defective in binding manganese and zinc does not inhibit microbial growth, unequivocally linking the antimicrobial properties of calprotectin to metal chelation. These results suggest that calprotectin contributes to host defense by rendering bacterial pathogens more sensitive to host immune effectors and reducing bacterial growth.


Subject(s)
Leukocyte L1 Antigen Complex/immunology , Neutrophils/immunology , Staphylococcus aureus/enzymology , Superoxide Dismutase/metabolism , Superoxides/metabolism , Animals , Anti-Bacterial Agents/immunology , Disease Models, Animal , Male , Manganese/metabolism , Mice , Mice, Inbred C57BL , Oxidative Stress , Staphylococcal Infections/immunology , Staphylococcal Infections/microbiology , Staphylococcus aureus/immunology , Zinc/metabolism
20.
FEBS Lett ; 584(23): 4717-24, 2010 Dec 01.
Article in English | MEDLINE | ID: mdl-21056039

ABSTRACT

Calmodulin(CaM)-regulated protein phosphorylation forms an important component of Ca(2+) signaling in animals but is less understood in plants. We have identified a CaM-binding receptor-like kinase from soybean nodules, GmCaMK1, a homolog of Arabidopsis CRLK1. We delineated the CaM-binding domain (CaMBD) of GmCaMK1 to a 24-residue region near the C-terminus, which overlaps with the kinase domain. We have demonstrated that GmCaMK1 binds CaM with high affinity in a Ca(2+)-dependent manner. We showed that GmCaMK1 is expressed broadly across tissues and is enriched in roots and developing nodules. Finally, we examined the CaMBDs of the five-member GmCaMK family in soybean, and orthologs present across taxa.


Subject(s)
Calcium-Calmodulin-Dependent Protein Kinases/chemistry , Calcium-Calmodulin-Dependent Protein Kinases/metabolism , Glycine max/enzymology , Amino Acid Sequence , Arabidopsis , Arabidopsis Proteins/chemistry , Calcium/metabolism , Calcium-Calmodulin-Dependent Protein Kinases/genetics , Calmodulin/metabolism , Cloning, Molecular , Conserved Sequence , DNA, Complementary/genetics , Gene Expression Regulation, Plant , Medicago truncatula , Molecular Sequence Data , Phosphorylation , Protein Structure, Tertiary , Sequence Homology, Amino Acid , Glycine max/genetics
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