ABSTRACT
In order to study the expression and the feasibility of scaled production of neuropeptide in the routine expression system such as E.coli with the pituitary adenylate cyclase activating polypep tide(PACAP) as an example, the following experiments were carried out. First, on the basis of the reported amino acid sequence of PACAP, DNA sequence of PACAP w as deduced and six partially complementary oligonucleotide fragments were design ed. The coding region of PACAP was obtained by renaturing the DNA fragments and ligation and identified by DNA sequencing. The coding region of PACAP was cloned into plasmid pGEX-4T-3 and transformed into E.coli BL21(DE3 ). An expression strain BLPACAP was selected. SDS-PAGE analysis revealed that t he GST-PACAP fusion protein was highly expressed and accumulated to about 30% o f the total bacterial proteins. By affinity chromatography, up to 90% GST-PACAP was purified by one step from bacterial lysate. The purified protein could prom ote neurite outgrowth of PC12 cells and the survival of spinal cord neurons.
ABSTRACT
ObjectiveExpression and purification of human tumor necrosis factorα(hTNFα)fusion protein with a stretch of six consecutive histidine residues(6×His) in E. coli.MethodshTNFα fusion proteins with 6×His at N and C terminus were expressed by using E. coli expression vectors pET- 28a(+) and pET-22b(+). The His6 tag allows the expression fusion protein purified in one step by immobilized metal Ni2+ chelation affinity chromatcgraphy in native state. Results The two construct expression vectors were expressed in E. coli respectively, the former with high level as insoluble protein, account for 45% of the total bacteria proteins and not purified; the later 8% as soluble protein, and characterized by SDS- PAGE, Westren-blot. By using affinity chromatography through Ni2+ - IDA Sepharose 6B, 100ml induction culture had 0.4mg hTNFα-6×His fusion proteins. Its purifity reached 90 %. ConclusionThe purification expression product can possess TNF activity and reach 5.42×104U/mg.
ABSTRACT
Objective To produce bioactive human bone morphogenetic protein-4 by Escherichia coli genetic engineering and investigate the effect of the product, recombinant BMP-4, on the bone marrow stem cells. Methods cDNA of human morphogenetic protein-4 mature peptide was obtained by RT PCR from tissue of human placenta. The gene was constructed in the pET-22b(+) expression vector and expressed in Escherichia coli BL-21 after transformation and induction by IPTG. The harvested protein was proved to be bioactive by inducing ectopic bone information in mouse thigh. The protein was applied to induce the cultured bone marrow stem cell. Shape change of the cell, ability of ALP (alkaline phosphatase) and concentration of OC (osteocalcin) were investigated. Results SDS-PAGE revealed a new protein band that located in position of 14?103 after 4 hours induction, the new protein made 15% of total bacteria protein, the rhBMP-4 could induce the cultured bone marrow stem cell of New Zealand rabbit to differentiate into osteoblasts and form calcified node. The ability of ALP and concentration of OC of tested group increased significantly than that of the control group. Conclusion The bioactive rhBMP-4 can be produced by Escherichia coli genic engineering, this protein can induce bone marrow stem cells to differentiate into osteoblast cells.
ABSTRACT
AFP from fetal serum and serum of patients with primary hepatic cancer were purified by affinity chromatography. Then, the lentil lectin-reactive and nonreactive variants of these purified glycoproteins were prepared by affinity chromatography with immobilized lectin. Glycopeptides and oligosaccharides were prepared from variants by protease treatment and hydrazinolysis, respectively, and subjected to carbohydrate and amino acid analysis. A small difference in the carbohydrate compositions of each variant was observed. Analysis of chemical compositions of AFP variants is useful for the differential diagnosis between benign liver diseases and primary hepatic cancer.