Identification of phosphatidic acid interacting proteins in Ganoderma lingzhi / 生物工程学报

Ganoderma lingzhi is widely recognized as a medicinal basidiomycetes. Triterpene acids (TAs) are the key bioactive medicinal components of G. lingzhi. Our previous studies have shown that phospholipid acid (PA) produced by phospholipase D (PLD) plays a regulatory role in TA synthesis. In order to further elucidate the molecular mechanism how PA regulates TA synthesis in G. lingzhi, PA beads enrichment combined with LC-MS/MS technology was used to identify PA interacting proteins in G. lingzhi. A total of 19 PA interacting proteins were identified, including cytochrome P450 monooxygenase (GL22084), specific protein kinase MAPK (GL23765), catalase and cell surface hydrophobicity-associated protein. GST tagged GL22084 and GL23765 proteins were obtained through gene cloning, heterologous expression, and purification. The interactions between GL22084/GL23765 and PA were verified by GST pull down assay. The identification of PA interacting proteins provides a basis for further understanding the molecular mechanism how PLD-mediated PA signaling molecules regulates the TA synthesis in G. lingzhi. Moreover, the PA interacting proteins identified in this study can also provide clues for the research of PLD/PA signaling pathway in other species.

Combination of mass spectrometry and GST pull-down techniques to study potential interacting protein of PCV2 ORF4 / 生物工程学报

A novel protein encoded by the open reading frame 4 (ORF4) was recently discovered in porcine circovirus type 2 (PCV2). However, little is known about the interaction proteins of ORF4 which hindered better understanding the biological functions of ORF4 in the life cycle of PCV2. In the present study, the ORF4 was inserted into the multiple cloning site of pCMV-N-Flag-GST, yielding recombinant plasmid pCMV-N-Flag-GST-ORF4. The recombinant plasmid was transfected into 293T cells and the intracellular interaction complex of ORF4 were enriched and separated by GST pull-down and SDS-PAGE, sequentially. The potential interacting proteins of PCV2 ORF4 were stained with silver and identified by mass spectrometry (MS). Finally, five candidate ORF4-interacting proteins, including Serine/threonine-protein phosphatase 6 catalytic subunit, alpha cardiac muscle 1, actin, SEC14-like protein 5 and myosin 9 were identified. These results would benefit a better understanding of the biological function of ORF4 in PCV2 infected cells.

Construction of a Mutant CaM-expressing Plasmid,and Expression,Purification,and Activity Identification of the Recombinant Protein / 中国医科大学学报

Objective To construct a CaME141G fusion protein-expressing plasmid,and to express,purify,and identify the activity of the recombinant protein. Methods The 141st site of the wild type CaM,E (GAG),was mutated to G (GGG),using site-specific mutagenesis technology. Escherichia coli BL-21 was transformed with the mutant plasmid. The GST-CaME141G fusion protein was mass-cultured and induced for expression. Subsequently,the GST-CaME141G fusion protein was purified using GS-4B beads. PreScission protease was applied to remove the GST,the Bradford method used to determine the concentration of purified protein,and SDS-PAGE used to detect its relative molecular weight and purity. The GST pull-down assay was used to study the protein's biological activity. Results The CaME141G protein was successfully purified at a high concentration and purity. The protein could interact with PreIQ protein fragments from the myocardial CaV1. 2 calcium channel C terminal,in a CaME141G concentration-dependent manner. Therefore,CaME141G has the ability to bind with the CaV1. 2 calcium channel. Conclusion This study successfully constructed a CaME141G fusion protein-expressing plasmid and purified the CaME141G protein. This lays a foundation for regulating the function of CaM mutations in the myocardial CaV1. 2 calcium channel,and for the study of its relationship with diseases of the cardiovascular system.

Construction of and Protein Preparation from a Recombinant Plasmid Containing the Distal Fragment of the Distal C-terminus of the Cav1.2 Channel / 中国医科大学学报

Objective To construct a recombinant plasmid vector containing the distal fragment of the distal C-terminus (dDCT) of the Cav 1.2 channel,and express,extract,and purify dDCT protein and characterize its biological activity.Methods dDCT cDNA was ligated into the pGEX-6p-1 vector to create a recombinant plasmid that was subsequently transformed into Escherichia coli BL21 competent cells.Expression of GST-dDCT fusion protein from this plasmid was induced with isopropy-β-D-thiogalactoside,and the resulting protein was purified using glutathione-sepharose 4B beads.The biological activity of dDCT was analyzed by GST pull-down assay.Results The recombinant plasmid was verified by restriction enzyme digestion and sequencing.The concentration and purity of the dDCT protein,which was extracted by ultrasonication,were high enough to detect dDCT activity.The binding of dDCT to CT1 was determined to be concentration-dependent.Conclusion The recombinant dDCT plasmid was successfully constructed,providing the fundamental basis for future studies on mechanisms of Cav 1.2 channel autoregulation.

Expression and Purification of an N?terminal Fragment of the Cav1.2 Calcium Channel and Characterization of Its Interaction with Calmodulin / 中国医科大学学报

Objective To investigate a method for the purification of the N?terminal peptide fragment(NT)of the myocardial calcium channel Cav1.2,and characterize its interaction with calmodulin(CaM). Methods EscherichiacoliBL?21 cells were transformed with plasmid pGEX?6p?3/NT harboring the NT?GST fusion gene. The cells harboring pGEX?6p?3/NT were cultured and protein expression was induced with isopropyl?β?D?thiogalactoside(IPTG). Then,the GST?NT fusion protein was purified by using glutathione Sepharose 4B(GS?4B)beads. GST was cleaved off with the PreScission protease,and SDS?PAGE was performed to detect the purity and relative molecular weight of the purified peptide. Further, GST pull?down assay was performed to characterize the interaction of the NT peptide with CaM. Results SDS?PAGE analysis showed that the NT peptide was successfully purified,with high purity. Results of the GST pull?down assay showed that the NT peptide could interact with CaM. Conclusion This study establishes a method for the purification of the NT peptide and lays the foundation for further research on the interaction partners and biological functions of NT.

Vector Construction,Protein Expression,Purification,and Identification of Calmodulin Mutants N2 and C2 / 中国医科大学学报

Objective To construct expression vectors of calmodulin(CaM)mutants N2 and C2,and to express,purify,and identify the mutant proteins,in order to study the interactions between CaM and calcium channels. Methods The cDNA of N?lobe and C?lobe of CaM were used to prepare the cDNA of N2 and C2. Next,the recombinant cDNAs were cloned into a pGEX?6p?3 plasmid,and the recombinant plasmids were trans?ferred into E.coli BL21 cells. The transfected BL21 cells were stimulated with IPTG. The fusion proteins were extracted by ultrasonication and puri?fied by using GS?4B beads. Finally,protein activity was identified by the pull?down assay. Results Both the restriction digestion map and the DNA sequence identification results confirmed that the recombinant plasmids were successfully constructed. SDS?PAGE results showed high purity and concentration of N2 and C2 proteins. Their activities and binding abilities with the calcium channel fragment were confirmed by the pull?down assay.Conclusion In this study,expression vectors of N2 and C2 are successfully constructed,and physiologically active N2 and C2 CaM mutant proteins are obtained.

Research of functional segments of chicken B-FA molecule binding with Ii chain / 中国免疫学杂志

Objective: To research the functional segments of B-FA molecule binding invariant chain and their characters. Methods:The DNA segments (α1α2, sα1α2 and α3TC ) of B-FA genes were respectively cloned and inserted into prokaryotic or eukaryotic expression plasmids,then they were singly or co-transfected with Ii gene into the engineering bacteria E. coli (BL-21)or 293T cells. After induction of expression,affinity chromatography and SDS-PAGE identification,the binding between B-FA segments and Ii molecule and co-localization in cells were observed with Pull-down and Western blot. Results:First three recombinant prokaryotic expression plasmids and four recombinant eukaryotic expression plasmids were constructed. The single molecules expressed by B-FA segments were observed after an affinity chromatography. Secondly the complexes of Ii/B-FA-α1α2 and Ii/B-FA-sα1α2 were detected by a Pull-down from the co-transfected corresponding prokaryotic expression plasmids,but no complex of Ii andα3TC,also in the western blot it was detected that B-FA-α1α2 or B-FA-sα1α2 as functional segment could bind Ii to form complex. Finally in eukaryotic expression 293T cells B-FA-sα1α2 kept localization, the same as B-FA. Conclusion: Chicken B-FA-α1α2 is function segment to bind with Ii molecule and keeps the location characters same as B-FA. The results of this research first time provide experimental evidence about B-FA functional region binding segment to Ii molecule.

Characters of location in cells and binding activity of chicken Ii and B-L gene ex-pressed products / 中国免疫学杂志

Objective:To study characters of the location in cells and binding activity of chicken Ii and B-L gene expressed products.Methods:The cloned gene segments of chicken Ii,B-LA and B-LB were respectively inserted into prokaryotic or eukaryotic expression plasmids,and then these recombinant plasmids were respectively alone transfected or cotransfected into engineering bacteria, Rosetta(DE3) or 293T cells.All of the recombinant bacteria were induced to express and their products then were renatured.The singly expressed products were detected to their immunogenicity with Western blot, and the co-expressed products were tested their binding with pull-down method and ( SDS-) PAGE.Results:First six of prokaryotic and eukaryotic recombinant expression plasmids were con-structed.The eukaryotic expressed products of Ii, B-LA and B-LB genes located in cellular plasma membrane.The single protein molecules were achieved from prokaryotic expressed products, which were renatured and purified with a Ni-column respectively.Secondly the prokaryotic expression Ii,B-LA and B-LB molecules could respectively induce mouse to product specific anti-bodies, which could recognize the corresponding products in eukaryotic expression.This indicated that they retained their antigenicity.Finally with pull-down from the products in co-expression in engineering bacteria and renaturation the Ii/B-LA or Ii/B-LB complexes were purified and the Ii,B-LA or B-LB monomers were dissociated from these complexes after a SDS treatment.Conclusion:The prokaryotic or eukaryotic expressed products of chicken Ii and B-L genes could retain their antigenicity,and chicken Ii could bind B-L molecules after prokaryotic coexpression and renaturation.These results provide a useful method to study the relation between Ii and MHC molecules.

Identification of interaction site of MIC2 with aldolase in Toxoplasma gondii / 中国人兽共患病学报

In this study ,we aim to identify the protein interaction site of microneme protein 2 (MIC2) and aldolase in Toxoplasma gondii .The tryptophan (Trp ,W) at site 767 of carboxyl terminus of MIC2 (MIC2C) was mutated into alanine (Ala ,A) by site-directed mutagenesis to construct plasmid MIC2C W/A/pGEX-4T-1 .The mutant protein GST-MIC2C W/A was expressed in E .coli upon IPTG induction .Glutathione sepharose beads were incubated with GST-MIC2C W/A and GST-MIC2C respectively ,then incubated with tachyzoite lysates ,and bound proteins were eluted using sample buffer .Eluants were resolved by SDS-PAGE and Western blot .A protein band specifically recognized by anti-aldolase antibody was detected in prod-ucts coming from GST pull-down of GST-MIC2C ,but not in pull-down products coming from GST-MIC2C W/A .With muta-tion of MIC2C W767 to A ,MIC2 protein lost the binding ability to aldolase .Tryptophan (W767 ) was the protein interaction site of MIC2 and aldolase in T .gondii .

Estrogen exerts the effect on stress-induced senescence of vascular smooth muscl cells in vitro / 解剖学报

Objective To explore the effects of estrogen on stress-induced senescence of vascular smooth muscle cells (VSMCs) and the underlying mechanisms. Methods The VSMCs of passage 2-3 cultured from female SD rats were induced into senescence by exposing to 150μmol/L H2O2 in the presence or absence of different concentrations(10-10mol/L-10-8mol/L) of 17β-estradiol (E2). The expressions or activities of senescence associated marker DcR2, senescence-associated beta-galactosidase (SA-β-Gal), oncogene Ras and p21WAF1 were detected by flow cytometry, cytochemical staining, pull-down assay or Western blotting analysis. Results Flow cytometry analysis showed that in the physiological concentrations, E2 significantly inhibited the H2O2-promoted high-level expression of DcR2 of VSMCs in a dose-dependent manner, with a highest inhibitive rate at 14.48%±0.6%(E2=10-8 mol/L;P<0.05, n =3);this inhibitive effect could be blocked by a E2 receptors inhibitor ICI 182,780. Cytochemistry staining showed that the rate of SA-β-Gal positive VSMCs induced by H2O2 decreased in presence of 10-8mol/L E2 (20.5%±1.4% vs 9.6%±0.9%;P<0.05, n =9). Pull-down assay and Western blotting analysis revealed that administration of 10-8mol/L E2 obviously reduced the H2O2-induced activity of Ras (0.60±0.06 vs 0.26±0.04;P<0.05, n =3) and expression of p21WAF1 (0.46±0.04 vs 0.33±0.02;P<0.05, n =3). Conclusion E2 exerts, an inhibitive effects on stress-induced senescence of VSMCs by suppressing the activity of Ras and expression of p21WAF1. This finding suggests a novel mechanism for the hormone's anti-atheroschlerotic effects.

Studies on The Interactions Between NIRF and P53 / 生物化学与生物物理进展

HEK293 or HeLa cells were transfected by NIRF and, or P53, whole cell extracts andimmunoprecipitates were subjected to SDS-PAGE followed by Western blotting. GST pull-down was carried outto identify the interactions between NIRF and P53. In vitro ubiquitination reaction was carried out to identify P53ubquitinate by NIRF. The results suggested that NIRF could interact with P53 in vivo and in vitro. The results alsoshowed that NIRF could ubiquitinate P53 in vivo and in vitro. The results indicated that NIRF would be a newnegative regulator of P53.

The molecular interaction between P53 and telomeric repeat binding protein 1 in vitro / 北京大学学报(医学版)

Objective: Cellular proliferate inhibition, senescence or apoptosis are induced by telomere shortening through the activation of P53 pathway, but so far, little is known of the mechanism. This study aimed to clarify the molecular regulation of P53 through telomere pathway by the investigation of molecular interaction between P53 and the main telomere associated protein telomeric repeat binding protein 1(TRBP1) in vitro. Methods: Glutathione S-transferase (GST) alone and 4 different human P53-GST fusion proteins were expressed in E. coli. and purified through glutathione Sepharose TM 4B by affinity chromatography, P53s were wild type P53 (1-393), N terminal truncated form P53 2C (95-393), C terminal truncated form P53 N5 (2-293) and single amino acid mutant P53 R175H (175 arginine to histidine). Glutathione Sepharose TM 4B, purified GST alone and P53 fusions were mixed with human breast cancer cell line MCF-7 cellular protein extracts through in vitro binding assay-pull down, the molecular interaction between P53 and TRBP1 were detected by Western blot. Results: SDS-PAGE and Coomassie brilliant blue staining showed that the molecular weights of all the purified proteins were as expected and purities were over 90%. Western blot of TRBP1 showed that both wild type P53 and P53 R175H could bind to TRBP1 of MCF-7 cells, and their binding capacities are similar, whereas GST alone and Glutathione Sepharose TM 4B beads couldn’t. Compared with both of them, the interaction between P53 2C and TRBP1 enhanced dramatically, but between P53 N5 and TRBP1 reduced significantly.Conclusion: P53 can interact with TRBP1 directly and in vitro, C terminus of P53 (293-393) is the structural domain of their interaction. This C terminus domain dependent interaction between P53 and TRBP1 may be related to the cellular activities induced by telomere dynamic changing.