Screening, Identifying and Function Analysis of Polyketide Synthase I Cluster from the Environmental Strain X-2 Which Produce Macrolactins / 微生物学通报

Macrolactins are 24-membered macrolides produced by unidentified marine bacterium, Actinomadura sp. and Bacillus sp., which exhibit both antibacterial and antitumor activities in vitro. The environmental strain X-2 which was isolated from the sediment of the East China Sea produce Macrolatin A, B and O. In this study, a set of degenerate oligonucleotide primers, designed for amplification ketosynthase(KS) domains, had been employed to identify KS gene fragments of the X-2 DNA samples. One 645 bp KS fragment(GenBank accession no. EF486351)had been cloned and used as a probe to screen the genome DNA fosmid library of X-2. Three positive clones were selected and sequenced, Homologous analysis and the function prediction of the obtained PKS gene fragments suggested that macrolactin is the Polyketide Biosynthesis Product of the gene cluster obtained in the environmental strain X-2.

Expression of Tumstatin_(183-230)-TRAIL fusion protein and identification of its biological functions / 第二军医大学学报

Objective:To express Tumstatin_(183-230)-TRAIL fusion protein and to observe its biological functions.Methods: SOE-ing PCR was employed to amplify the recombinant sequence of Tumstatin_(183-230)and TNF-related apoptosis-inducing ligand (TRAIL_(114-281)).An expression vector pMAL-Tu-T was constructed by inserting Tu-T sequence into pMAL-c_2;the vector was used to transfect E.coli BL21(DE3)and expression of MBP-Tu-T fusion protein was induced by IPTG.Amylose Resin columns were employed to purify the fusion protein.The biological functions of MBP-Tu-T protein was examined by inhibitory test of endothelial cell proliferation,standard tumor cell cytotoxic assay,in vitro tube formation inhibition,and electron microscopic observation(apoptosis).Results:The expression rate of MBP-Tu-T fusion protein in E.coli was about 20%. Purified recombinant protein obviously inhibited endothelial cell proliferation(IC_(50)12.5?g/ml),induced apoptosis of pancreatic cancer cells,and inhibited tube formation.Conclusion:Constructed MBP-Tu-T fusion protein is bifunctional,which lays a solid foundation for further investigation of antitumor effect of Tumstatin_(183-230)-TRAIL in vivo.