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1.
Biochim Biophys Acta Mol Cell Res ; 1870(8): 119567, 2023 12.
Artigo em Inglês | MEDLINE | ID: mdl-37582439

RESUMO

Liquid-liquid phase separation (LLPS) appears to be a newly appreciated aspect of the cellular organization of biomolecules that leads to the formation of membraneless organelles (MLOs). MLOs generate distinct microenvironments where particular biomolecules are highly concentrated compared to those in the surrounding environment. Their thermodynamically driven formation is reversible, and their liquid nature allows them to fuse with each other. Dysfunctional biomolecular condensation is associated with human diseases. Pathological states of MLOs may originate from the mutation of proteins or may be induced by other factors. In most aberrant MLOs, transient interactions are replaced by stronger and more rigid interactions, preventing their dissolution, and causing their uncontrolled growth and dysfunction. For these reasons, there is great interest in identifying factors that modulate LLPS. In this review, we discuss an enigmatic and mostly unexplored aspect of this process, namely, the regulatory effects of metal ions on the phase behavior of biomolecules.


Assuntos
Organelas , Proteínas , Humanos , Organelas/metabolismo , Proteínas/metabolismo
2.
Cell Commun Signal ; 21(1): 92, 2023 05 04.
Artigo em Inglês | MEDLINE | ID: mdl-37143076

RESUMO

RXRß is one of three subtypes of human retinoid X receptor (RXR), a transcription factor that belongs to the nuclear receptor superfamily. Its expression can be detected in almost all tissues. In contrast to other subtypes - RXRα and RXRγ - RXRß has the longest and unique N-terminal sequence called the AB region, which harbors a ligand-independent activation function. In contrast to the functional properties of this sequence, the molecular properties of the AB region of human RXRß (AB_hRXRB) have not yet been characterized. Here, we present a systematic biochemical and biophysical analysis of recombinant AB_hRXRB, along with in silico examinations, which demonstrate that AB_hRXRB exhibits properties of a coil-like intrinsically disordered region. AB_hRXRB possesses a flexible structure that is able to adopt a more ordered conformation under the influence of different environmental factors. Interestingly, AB_hRXRB promotes the formation of liquid-liquid phase separation (LLPS), a phenomenon previously observed for the AB region of another human subtype of RXR - RXRγ (AB_hRXRG). Although both AB regions seem to be similar in terms of their ability to induce phase separation, they clearly differ in the sensitivity to factors driving and regulating LLPS. This distinct LLPS response to environmental factors driven by the unique amino acid compositions of AB_hRXRB and AB_hRXRG can be significant for the specific modulation of the transcriptional activation of target genes by different subtypes of RXR. Video Abstract.


Assuntos
Proteínas Intrinsicamente Desordenadas , Receptores Citoplasmáticos e Nucleares , Humanos , Receptores X de Retinoides/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Regulação da Expressão Gênica , Ativação Transcricional , Proteínas Intrinsicamente Desordenadas/metabolismo
3.
Front Nutr ; 10: 1330307, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38292698

RESUMO

The purpose of this study was to determine the sensory profile of honeys based on the method of quantitative descriptive analysis and principal component analysis and assess consumer preferences of raw and pasteurized honeys. Samples of multi-floral honeys (from the store and apiary) were subjected to sensory analysis based on the method of ranking for taste preference, the method of scaling based on color, aroma, taste, and texture, and the method of differential descriptive analysis using 11 quality descriptors. The results were subjected to statistical analysis using the Principal Component Analysis method. The taste was found to be a descriptor that differentiates honey by origin. Consumers prefer the taste of pasteurized honeys. As a result of assessing the quality of honeys using the scaling method, it was found that: raw honeys are characterized by a lighter color than pasteurized honeys, store-bought honeys have a less noticeable aroma than honeys obtained from beekeepers, while samples of pasteurized honeys were judged to have a consistency more like that of typical honey. The sensory profiles obtained highlight the differences between pasteurized honeys and raw honeys.

4.
Biomolecules ; 12(9)2022 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-36139105

RESUMO

Some animal organs contain mineralized tissues. These so-called hard tissues are mostly deposits of calcium salts, usually in the form of calcium phosphate or calcium carbonate. Examples of this include fish otoliths and mammalian otoconia, which are found in the inner ear, and they are an essential part of the sensory system that maintains body balance. The composition of ear stones is quite well known, but the role of individual components in the nucleation and growth of these biominerals is enigmatic. It is sure that intrinsically disordered proteins (IDPs) play an important role in this aspect. They have an impact on the shape and size of otoliths. It seems probable that IDPs, with their inherent ability to phase separate, also play a role in nucleation processes. This review discusses the major theories on the mechanisms of biomineral nucleation with a focus on the importance of protein-driven liquid-liquid phase separation (LLPS). It also presents the current understanding of the role of IDPs in the formation of calcium carbonate biominerals and predicts their potential ability to drive LLPS.


Assuntos
Proteínas Intrinsicamente Desordenadas , Animais , Biomineralização , Cálcio/metabolismo , Carbonato de Cálcio , Proteínas Intrinsicamente Desordenadas/metabolismo , Mamíferos/metabolismo , Membrana dos Otólitos/metabolismo , Sais
5.
Biomolecules ; 12(7)2022 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-35883463

RESUMO

Liquid-liquid phase separation (LLPS) of biomolecules has emerged as a new paradigm in cell biology, and the process is one proposed mechanism for the formation of membraneless organelles (MLOs). Bacterial cells have only recently drawn strong interest in terms of studies on both liquid-to-liquid and liquid-to-solid phase transitions. It seems that these processes drive the formation of prokaryotic cellular condensates that resemble eukaryotic MLOs. In this review, we present an overview of the key microbial biomolecules that undergo LLPS, as well as the formation and organization of biomacromolecular condensates within the intracellular space. We also discuss the current challenges in investigating bacterial biomacromolecular condensates. Additionally, we highlight a summary of recent knowledge about the participation of bacterial biomolecules in a phase transition and provide some new in silico analyses that can be helpful for further investigations.


Assuntos
Eucariotos , Organelas , Espaço Intracelular , Transição de Fase
6.
Int J Mol Sci ; 22(23)2021 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-34884563

RESUMO

Eukaryotic cells are composed of different bio-macromolecules that are divided into compartments called organelles providing optimal microenvironments for many cellular processes. A specific type of organelles is membraneless organelles. They are formed via a process called liquid-liquid phase separation that is driven by weak multivalent interactions between particular bio-macromolecules. In this review, we gather crucial information regarding different classes of transcription regulators with the propensity to undergo liquid-liquid phase separation and stress the role of intrinsically disordered regions in this phenomenon. We also discuss recently developed experimental systems for studying formation and properties of membraneless organelles.


Assuntos
Fenômenos Fisiológicos Celulares , Proliferação de Células , Células Eucarióticas/fisiologia , Proteínas Intrinsicamente Desordenadas/metabolismo , Organelas/fisiologia , Fatores de Transcrição/metabolismo , Animais , Humanos
7.
Comput Struct Biotechnol J ; 19: 4300-4318, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34429849

RESUMO

Nucleobindin-2 (Nucb2) is a protein that has been suggested to play roles in a variety of biological processes. Nucb2 contains two Ca2+/Mg2+-binding EF-hand domains separated by an acidic amino acid residue-rich region and a leucine zipper. All of these domains are located within the C-terminal half of the protein. At the N-terminal half, Nucb2 also possesses a putative Zn2+-binding motif. In our recent studies, we observed that Nucb2 underwent Ca2+-dependent compaction and formed a mosaic-like structure consisting of intertwined disordered and ordered regions at its C-terminal half. The aim of this study was to investigate the impact of two other potential ligands: Mg2+, which possesses chemical properties similar to those of Ca2+, and Zn2+, for which a putative binding motif was identified. In this study, we demonstrated that the binding of Mg2+ led to oligomerization state changes with no significant secondary or tertiary structural alterations of Nucb2. In contrast, Zn2+ binding had a more pronounced effect on the structure of Nucb2, leading to the local destabilization of its N-terminal half while also inducing changes within its C-terminal half. These structural rearrangements resulted in the oligomerization and/or aggregation of Nucb2 molecules. Taken together, the results of our previous and current research help to elucidate the structure of the Nucb2, which can be divided into two parts: the Zn2+-sensitive N-terminal half (consisting of nesfatin-1 and -2) and the Ca2+-sensitive C-terminal half (consisting of nesfatin-3). These results may also help to open a new discussion regarding the diverse roles that metal cations play in regulating the structure of Nucb2 and the various physiological functions of this protein.

8.
Int J Biol Macromol ; 183: 936-949, 2021 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-33971237

RESUMO

Nuclear receptors (NRs) are a family of transcription factors that are regulated endogenously by small lipophilic ligands. Recently, liquid-liquid phase separation (LLPS) has appeared as a new aspect of NR function. In the human retinoid X receptor γ (hRXRγ), the inherently disordered AB region undergoes LLPS via homotypic multivalent interactions. To better understand the functions of liquid condensates, a clear view of the molecular interactions underlying the LLPS are required. The phase separation propensity of the AB region of hRXRγ (AB_hRXG) at a high NaCl concentration, a lower critical solution temperature behavior, and also sensitivity to kosmotropic salts and 1,6-hexanediol, which all indicate the importance of hydrophobic interactions in the formation of AB_hRXG liquid condensates, is presented in the paper. Additionally, molecular crowding agents and TMAO shift the equilibrium, in turn enabling phase transition at lower AB_hRXG concentrations. Although the LLPS of the proteins can lead to aggregation, AB_hRXG liquid condensates are not aggregation prone. Interestingly, the formation of AB_hRXG liquid condensates has an impact on the rest of the receptor, as AB_hRXG liquid condensates recruit the remaining fragment of hRXRγ into the droplets. The ability of AB_hRXG to undergo LLPS might be important for gene expression regulation.


Assuntos
Proteínas Intrinsicamente Desordenadas/química , Receptores X de Retinoides/química , Humanos , Interações Hidrofóbicas e Hidrofílicas , Temperatura
9.
J Steroid Biochem Mol Biol ; 198: 105571, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31881311

RESUMO

The retinoid X receptor (RXR) is a member of the nuclear receptor (NR) superfamily that occupies the central position among other NRs by forming both homodimers and heterodimers with other representatives of the family. RXR shares similar structural domains with other members of NRs. The major differences in the subtypes and isoforms of RXR are in the AB region. To date, there have been no data concerning the molecular properties of the AB region of hRXRγ (AB_hRXG). Here, we describe the biochemical and biophysical properties of the recombinant AB_hRXG. The results indicate that AB_hRXG shows the structural and functional characteristics of the pre-molten globule-like (PMG-like) group of intrinsically disordered proteins (IDPs) and also has a significant propensity for folding. We also present the first experimental evidence showing that the AB region of NRs promotes the formation of liquid-liquid phase separation (LLPS).


Assuntos
Proteínas Intrinsicamente Desordenadas/química , Receptor X Retinoide gama/química , Dicroísmo Circular , Simulação por Computador , Humanos , Extração Líquido-Líquido , Ligação Proteica , Desnaturação Proteica , Dobramento de Proteína , Multimerização Proteica , Estrutura Secundária de Proteína , Temperatura
10.
PLoS One ; 11(8): e0160536, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27501389

RESUMO

Ageing and mutations of transthyretin (TTR), the thyroid hormones and retinol transporting protein lead to amyloidosis by destabilizing the structure of TTR. Because protein structure is regulated through posttranslational modifications, we investigated the Small Ubiquitin-like Modifier (SUMO)ylation of TTR. We chose the widely used Ubc9 fusion-directed SUMOylation system, which is based on a fusion of the SUMOylation substrate of interest with Ubc9, a sole SUMO conjugating enzyme. Surprisingly, despite our presumptions, we found that Ubc9 fused to TTR was SUMOylated at a unique set of lysine residues. Three unknown SUMOylation sites of Ubc9-K154, K18 and K65-were revealed by mass spectrometry (MS). The previously reported SUMOylation at K49 of Ubc9 was also observed. SUMOylation of the lysine residues of TTR fused to Ubc9 was hardly detectable. However, non-fused TTR was SUMOylated via trans-SUMOylation by Ubc9 fused to TTR. Interestingly, mutating the catalytic residue of Ubc9 fused to TTR did not result in complete loss of the SUMOylation signal, suggesting that Ubc9 linked to TTR is directly cross-SUMOylated by the SUMO-activating enzyme E1. Ubc9, TTR or fusion proteins composed of TTR and Ubc9 specifically affected the global SUMOylation of cellular proteins. TTR or Ubc9 alone increased global SUMOylation, whereas concomitant presence of TTR and Ubc9 did not further increase the amount of high-molecular weight (HMW) SUMO conjugates. Our data suggest that TTR may influence the SUMOylation of Ubc9, thereby altering signalling pathways in the cell.


Assuntos
Pré-Albumina/metabolismo , Enzimas de Conjugação de Ubiquitina/metabolismo , Células HEK293 , Humanos , Lisina/metabolismo , Mutagênese Sítio-Dirigida , Pré-Albumina/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Sumoilação , Enzimas de Conjugação de Ubiquitina/genética
12.
Chem Commun (Camb) ; 49(46): 5271-3, 2013 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-23632824

RESUMO

We report on the activation of CO2 by the well-defined alkylzinc hydroxide (tBuZnOH)6 in the absence and presence of tBu2Zn as an external proton acceptor. The slight modifications in reaction systems involving organozinc precursors enable control of the reaction products with high selectivity leading to the isolation of the mesoporous solid based on ZnCO3 nanoparticles or an unprecedented discrete alkylzinc carbonate [(tBuZn)2(µ5-CO3)]6 cluster with the Zn-C bond intact, respectively.

13.
Chemistry ; 18(18): 5637-45, 2012 Apr 27.
Artigo em Inglês | MEDLINE | ID: mdl-22431330

RESUMO

We report on investigations of reactions of tBu(2)Zn with 8-hydroxyquinoline (q-H) and the influence of water on the composition and structure of the final product. A new synthetic approach to photoluminescent zinc complexes with quinolinate ligands was developed that allowed the isolation of a series of structurally diverse and novel alkylzinc 8-hydroxyquinolate complexes: the trinuclear alkylzinc aggregate [tBuZn(q)](3) (1(3)), the pentanuclear oxo cluster [(tBu)(3)Zn(5)(µ(4) -O)(q)(5)] (2), and the tetranuclear hydroxo cluster [Zn(q)(2)](2)[tBuZn(OH)](2) (3). All compounds were characterized in solution by (1)H NMR, IR, UV/Vis, and photoluminescence (PL) spectroscopy, and in the solid state by X-ray diffraction, TGA, and PL studies. Density functional theory calculations were also carried out for these new Zn(II) complexes to rationalize their luminescence behavior. A detailed analysis of the supramolecular structures of 2 and 3 shows that the unique shape of the corresponding single molecules leads to the formation of extended 3D networks with 1D open channels. Varying the stoichiometry, shape, and supramolecular structure of the resulting complexes leads to changes in their spectroscopic properties. The close-packed crystal structure of 1(3) shows a redshifted emission maximum in comparison to the porous crystal structure of 2 and the THF-solvated structure of 3.

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