| Insulin-like Growth Factor I (IGF-I) was a multifunctional growth factor which was firstly found in blood serum. It was confirmed to promote the proliferation and differentiation and growth of kinds of cells, and also the breeding and performance of animals. It was a very important factor in the therapeutic treatment and the recovery of many diseases. IGF-I was rare in the serum, so it was very difficult to extract it from blood. Expression of IGF-I in vitro was needed to fulfill the demand from the foundation investigation and clinic applicant.Prokaryotic and eukaryotic expression system were used in this experiment to express porcine insulin-like growth factor I (pIGF-I). Polymerase Chain Reaction (PCR) cloning and splicing of objective gene were used in prokaryotic and eukaryotic expression system respectively. The genes of pIGF-I were cloned into prokaryotic expression vector pGEX-KG and eukaryotic expression vector pPIC9K, and the expression of the gene was studied, which settle the foundation of the supply of pIGF-I protein for foundation investigation and clinic applicant.A prokaryotic expression vector containing pIGF-I was constructed, and fusion protein of GST-pIGF-I was obtained. Two pieces of specific primer were designed to amplify signal peptide and mature protein of pIGF-I from a vector which pIGF-I cDNA had already been inserted. The product with PCR was digested, also the vector pGEX-KG, and T4 ligase was used to connect each other. The vector was confirmed with PCR and enzyme digesting and sequencing. The recombinant vector was transformed into the host cells E. coli BL21 (λDE3). The positive clone was cultured and induced with Isopropy-β-D-Thiogalactoside (IPTG), and SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) analysis of the supernanant of the cell lysate suggested a new protein band about 37 kDa was detected. The results demonstrated that pKG-IGF-I expression vector had been constructed successfully...
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