The formation of most proteins consists of two steps: the synthesis of precursor proteins and the synthesis of functional proteins. In these processes, propeptides play important roles in assisting protein folding or inhibiting its activity. As an important polypeptide chain coded by a gene sequence in lipase gene, propeptide usually functions as an intramolecular chaperone, assisting enzyme molecule folding. Meanwhile, some specific sites on propeptide such as glycosylated sites, have important effect on the activity, stability in extreme environment, methanol resistance and the substrate specificity of the lipase. Studying the mechanism of propeptide-mediated protein folding, as well as the influence of propeptide on lipases, will allow to regulate lipase by alternating the propeptide folding behavior and in turn pave new ways for protein engineering research.
Lipase/metabolism* ; Molecular Chaperones/metabolism* ; Protein Folding ; Protein Precursors ; Substrate Specificity

OBJECTIVE: To develop monoclonal antibodies that can specifically recognize human von Willebrand factor (VWF) propeptide (VWFpp) in plasma, and establish a rapid and reliable method for the detection of VWFpp antigen in plasma by using the double-antibody sandwich ELISA with the obtained anti-VWFpp monoclonal antibody. METHODS: The recombinant human VWFpp (D1 and D2 regions) protein expressed in eukaryotic cells was used as immunogen to immunize BALB/c mice with routine method, so as to obtain clones of fusion cells. After screening and identification, hybridoma cell lines secreting monoclonal antibodies against VWFpp were selected, and then double-antibody sandwich ELISA assay was used to construct VWFpp antigen detection kit for the determination of VWFpp in human plasma. The levels of VWFpp antigen in plasma of 12 leukemia patients who underwent bone marrow transplantation were dynamically detected. RESULTS: Two hybridoma cell lines that can be subcultured continuously and secrete monoclonal antibodies against VWFpp were obtained and named SZ175 and SZ176 respectively. Identified by ELISA and Western blot, the antibodies could both specifically recognize VWFpp but couldn't recognize mature VWF (without propeptide). Based on the principle of double-antibody sandwich ELISA, monoclonal antibodies SZ175 and SZ176 were successfully made into a kit for detecting VWFpp antigen. The plasma VWFpp levels of leukemia patients before and after bone marrow transplantation were dynamically detected. The results showed that the plasma VWFpp levels of the patients after transplantation were significantly higher than those before transplantation. CONCLUSION Two monoclonal antibodies against VWFpp were successfully prepared, and a double-antibody sandwich ELISA detection kit for VWFpp antigen was constructed, which provides a powerful tool for further study on the biological function of VWFpp, the clinical diagnosis and classification of von Willebrand disease (VWD), and the prognostic monitoring of endothelial injury-related diseases.
Animals ; Mice ; Humans ; von Willebrand Factor ; Antibodies, Monoclonal ; Protein Precursors/metabolism* ; von Willebrand Diseases/diagnosis* ; Prognosis

This article reviews the production, metabolism, and clinical application of procalcitonin (PCT). PCT is a useful indicator to differentiate bacterial infection and virus infection. Also, it can be used to determine the infection severity and prognosis.
Animals ; Bacterial Infections ; immunology ; Calcitonin ; genetics ; metabolism ; Calcitonin Gene-Related Peptide ; Humans ; Protein Precursors ; genetics ; metabolism ; Virus Diseases ; metabolism

Tumor necrosis factor (TNF) is a cytokine that is produced by immune cells in response to bacterial and viral stimuli and plays important roles in various inflammatory diseases. TNF is produced as a membrane-bound precursor, which is then cleaved to release soluble mature protein. We expressed murine pro-TNF in Saccharomyces cerevisiae and examined processing and cellular localization of the recombinant protein. Yeast cells were transformed with an expression construct carrying the pro-TNF gene under the control of alcohol dehydrogenase promoter. Immunoblotting analysis of cell homogenate revealed expression of 26 kD pro-TNF in transformed cells. Upon centrifugation, pro-TNF transformed cells fractionated into the membrane/particulate. In a clone that expresses a high level of pro-TNF, mature 17 kD TNF was detected in the culture medium, although the amount was far smaller than that of cell-associated pro-TNF. Flow cytometric analysis of yeast spheroplasts demonstrated the presence of TNF on the cell surface. Our results show that pro-TNF expressed in yeast mainly resides in the cellular membrane with an orientation similar to that of pro-TNF produced in mammalian cells. Our data suggest that the transformed yeast cells can be used for the genetic analysis of pro-TNF processing machinery in immune cells.
Animal ; Cell Line ; Cell Membrane/metabolism ; Flow Cytometry ; Immunoblotting ; Mice ; Plasmids ; Protein Precursors/metabolism* ; Protein Precursors/genetics ; Saccharomyces cerevisiae/metabolism* ; Saccharomyces cerevisiae/genetics ; Transformation, Genetic ; Tumor Necrosis Factor/metabolism* ; Tumor Necrosis Factor/genetics

OBJECTIVETo study the expression of AKAP82 which was one of A-kinase anchor proteins in sperm in asthenospermia.

METHODSSperm from 41 patients with asthenospermia (experimental group) and 27 healthy fertile men (control group). Motility parameters were estimated with a computer-assisted semen analysis (CASA) technique. Electrophoretic and immunoblot analysis and indirect immunofluorescence of sperm were assayed in experimental group and control group respectively.

RESULTSEleven cases in experimental group showed abnormal bands or deletion of normal band in immunoblot analysis, 2 of which were also abnormal in immunofluorescence results, and while only 2 abnormal in the control. A significant difference between experimental and control group was observed (P < 0.05).

CONCLUSIONAbnormality of AKAP82 expression in sperm may be one of the etiological factors in asthenospermia.

Adult ; Animals ; Blotting, Western ; Fluorescent Antibody Technique, Indirect ; Humans ; Male ; Oligospermia ; metabolism ; Protein Precursors ; biosynthesis ; Rabbits ; Sperm Motility ; Spermatozoa ; metabolism

OBJECTIVETo screen proteins in hepatocytes interacting with HBeAg transactivated protein (HBeAgTP) with yeast-two hybrid technique for investigating the biological functions of HBeAgTP.

METHODSSuppression subtractive hybridization (SSH) and bioinformatics techniques were used for screening and cloning of the target genes transactivated by HBeAg. The HBeAgTP gene was amplified by polymerase chain reaction (PCR) and HBeAgTP bait plasmid was constructed with yeast-two hybrid system 3, and then transformed into yeast AH109. The transformed yeast mated with yeast Y187 containing liver cDNA library plasmid in 2 x YPDA medium. Diploid yeast was plated on synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) and synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) containing X-gal for selecting two times and screening. After extracting and sequencing of plasmid from blue colonies, the results were analyzed by bioinformatics.

RESULTSHBeAgTP gene was successfully cloned and expressed in yeast cells. Fifteen genes in twenty-four positive colonies were obtained using yeast-two hybrid technique.

CONCLUSIONHBeAgTP conjugated protein genes were successfully cloned, along with the genes involved in transcription and translation of proteins, immunoloregulation, materials and energy metabolism in vivo.

Hepatitis B e Antigens ; genetics ; metabolism ; Hepatitis B virus ; immunology ; Hepatocytes ; immunology ; metabolism ; Humans ; Protein Interaction Mapping ; Protein Precursors ; genetics ; metabolism ; Two-Hybrid System Techniques ; Yeasts ; genetics

Animals ; Cell Differentiation ; Hepatocyte Growth Factor ; genetics ; metabolism ; Membrane Proteins ; genetics ; metabolism ; Mice ; Mouse Embryonic Stem Cells ; cytology ; metabolism ; Protein Precursors ; genetics ; metabolism ; Serine Endopeptidases ; genetics ; metabolism

OBJECTIVETo screen proteins in leukocytes interacting with PS1TP2 by yeast-two hybrid and to view their subcellular localization in HepG2 cells.

METHODSThe function and structure of PS1TP2 were studied by bioinformatic analysis. PS1TP2 gene was amplified and cloned into plasmid pET32a (+) and pGBKT7 to construct recombinant expression vectors pET32a (+)-PS1TP2 and pGBKT7-PS1TP2. They were transduced into E. coli Rosetta strain and yeast AH109. The transformed yeast mated with yeast Y187 containing leukocyte cDNA library plasmid in a 2xYPDA medium. Diploid yeast cells were plated on a synthetic dropout nutrient medium (SD/-Trp-Leu-His-Ade) for selecting twice and then screening. Then a green fluorescent protein (GFP) expression vector pEGFP-C1-PS1TP2 was established, transduced into HepG2, and its subcellular localization was studied by fluorescence microscopy and confocal microscopy.

RESULTSBioinformatic analysis showed that the PS1TP2 gene was located at 6q24.1, the protein was unstable and the aliphatic index was very high. After transformation of the E. coli and yeast AH109, the expression protein showed: (1) the molecular weight of the expressed product was about 41000 Da, and (2) PS1TP2 existed within the cells. Diploid yeast cells were plated on the synthetic dropout nutrient medium containing X-a-gal for selecting twice and then screening. Twenty-six colonies from blue colonies were sequenced, pEGFP-C1-PS1TP2 was successfully expressed in the HepG2 cells, and PS1TP2 was located in the cell plasma.

CONCLUSIONA prokaryotic expression vector pET32a(+)-PS1TP2 was constructed successfully and the PS1TP2 was successfully expressed in the yeast system. Genes of PS1TP2 interact with leukocyte proteins. These results bring some new clues for studying the biological functions of HBV.

Base Sequence ; Cloning, Molecular ; Dipeptides ; Gene Expression ; Hep G2 Cells ; Hepatitis B Surface Antigens ; metabolism ; Humans ; Protein Precursors ; metabolism ; Proteins ; genetics ; metabolism ; Two-Hybrid System Techniques

Nerve growth factor (NGF) promotes neuronal survival and differentiation and stimulates neurite outgrowth. NGF is synthesized as a precursor-proNGF in vivo. In this paper, a pET-proNGF prokaryocyte expression vector was constructed and transformed into E. coli BL21(DE3)pLysS. The proNGF was expressed in the form of non-active aggregated monomer in E. coli after induction with IPTG. SDS-PAGE revealed the proNGF expression product had a Mr.30.2 kD. Western blotting analysis showed that the protein had good antigenicity. Fusion protein was successfully purified by Ni2+-NTA affinity chromatography and cleaved by Enterokinase and 13.1 mg proNGF was obtained from 100 mL cell culture in a typical experiment. The protein was dialyzed in a redox system containing reduced and oxidized glutathione. RP-HPLC was used to analysis the result of the refolding. The refolded proNGF protein can induce neurite outgrowth of PC12 cells, which indicated that pro-form of NGF we obtained had biological activity.
Escherichia coli ; genetics ; metabolism ; Genetic Vectors ; genetics ; Humans ; Nerve Growth Factor ; biosynthesis ; genetics ; Protein Precursors ; biosynthesis ; genetics ; Protein Renaturation ; Recombinant Fusion Proteins ; biosynthesis ; genetics ; isolation & purification

BACKGROUNDProneurotrophins such as the precursor of nerve growth factor (proNGF) and the precursor of brain-derived neurotrophic factor (proBDNF) interacted with sortilin and p75(NTR) to form a complex capable of activating an apoptotic signaling. We found that the expression of p75(NTR) and sortilin was increased in ischemic retina induced by elevated intraocular pressure (IOP), but the protein expression changes of proNGF and proBDNF in the same situation were not clear. This study aimed to ascertain the protein expression changes of proNGF and proBDNF in ischemic retina induced by elevated IOP.

METHODSExpression of proBDNF and proNGF was examined by double-labeling immunochemistry in normal rat retina, examined using Western blotting and analyzed using statistical methods in ischemic retina induced by elevated IOP.

RESULTSImmunocytochemistry showed that the proBDNF expressed in the ganglion cell layer (GCL) while the proNGF primarily existed in both the nerve fiber layers (NFL) and large ganglion cell bodies of normal rat retina. Western blotting analysis demonstrated that the molecule weights of 28 kD (proBDNF)/25 kD (proNGF) band were increased significantly (P < 0.05) at days 3, 5 and 7 after retinal elevated-IOP-induced ischemia.

CONCLUSIONProBDNF expressed in the GCL and proNGF primarily presented in NFL and large ganglion cell bodies of normal rat retina, the protein expression forms of 28 kD proBDNF and 25 kD proNGF increased in ischemic retina induced by elevated IOP.

Animals ; Blotting, Western ; Brain-Derived Neurotrophic Factor ; analysis ; Immunohistochemistry ; Intraocular Pressure ; physiology ; Ischemia ; metabolism ; Male ; Nerve Growth Factor ; analysis ; Protein Precursors ; analysis ; Rats ; Rats, Wistar ; Retinal Diseases ; metabolism