Expression Of Human Prostate Specific Antigen In Escherichia Coli And Production Of Anti-PSA

Prostate specific antigen (PSA) is a kallikrein family member with serine protease activity commonly used as a diagnostic marker in the early diagnosis and monitoring of prostate cancer. PSA is a 33–34 kD protease and is secreted by the luminal epithelial cells of the prostate gland into seminal fluid . PSA mediates the liquefaction of semen by causing the degradation of semenogelin I and II, and fibronectin. PSA can also cleave a variety of other proteins including insulin-like growth factor (IGF) binding protein-3(IGFBP-3), resulting in increased availability of IGF in tumors. The precise relationship between the reported functions of PSA in prostate tumor cells in vitro and the biological role of PSA as a protease in human prostate cancer in vivo remains unclear. The PSA applied in clinical diagnosis and therapy was extracted from seminal fluid so far. This method makes PSA costly and not be able to supply the market enough, furthermore the key material-seminal fluid which was obtained from volunteers may be a possible infectious agent. So it is very important to establish a genetic engineering method to produce PSA.Due to the advantages of producing recombinant protein in E.coli, such as low cost, short period and being carcinogenic-gene-free, E.coli is becoming the main tool used in gene engineering to produce cytokine and peptide medicine. While most heterogenous genes are likely to express proteins in the form of inclusion body in E.coli, which leaves protein refolding difficulty and cost increased, and the activity of refolding protein commonly is not high .To obtain the recombinant protein in E.coli with high solibility, based on the published result about Dsb family, we successfully constructed the coexpression vector, pET-S1-S2-PSA, which can express PSA in a soluble form. We first constructed the vector, and then optimized the expression condition, achieving the expression of the recombinant protein in soluble form. And we utilized the PSA fusion protein to immunize rabbits, and obtained anti-PSA rabbit serum which can be used as a diagnostic reagent.Our results may be applied in the prokaryotic expression of many other cytokines and peptides. It may also contribute to the research on prokaryotic expression mechanism.