[Construction and characterization of the chimeric protein consisting RGD-containing peptide and proUK]

On the basis of structure analysis and computer modeling of proUK, two-chain DNA fragment encoding RGD peptide was inserted into the corresponding proUK cDNA site between Gly118-Leu119, using site-directed mutagenesis and DNA recombinant techniques. The chimeric gene was expressed in methylotrophic yeast Pichia pastoris expression system. The chimeric protein was purified after two step purification of Zn2+ chelating column and SP cation exchange column. The specific activity was 65,000 IU/mg protein. The chimeric protein had somewhat lower catalytic efficiency (kcat/Km) on the substrate S2444 as compared to Urokinase. But it had high anti-platelet aggregation activity, and the half inhibit constant was 2.1 mumol/L. The results showed that the chimeric protein not only had higher thrombolytic activity but also obtained anti-thrombus function. Further evaluation of the thrombolytic and antithrombolytic potential in appropriate animal models seemed to be investigated.

[Application of a gel chromatography renaturing way on low molecular single-chain urokinase mutant(DscuPA-32K)]

A recombinant mutant gene with thrombolytic and antithrombolytic bifunction was expressed in E. coli. Owing to two reasons of high molecular weight and over expression, dscuPA existed in inclusion body form. The protein of inclusion body was inactive protein. In order to obtain active protein, inclusion bodies should be denatured and then renatured. We performed a novel way named gel-chromatography column renaturation way. Compare with traditional renaturation way, this refolding approach had some obvious advantages, such as low cost and high recovery, and accomplished the preliminary purification step of desired protein(DscuPA-32K). Especially to proteins that easily became inactive and degradation, this approach might have good prospect.