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v-Src is a non-receptor protein tyrosine kinase involved in many signal transduction pathways and closely related to the activation and development of cancers. We present here the expression, purification, and bioactivity of a GST (glutathione S-transferase)-fused v-Src from a bacterial expression system. Different culture conditions were examined in an isopropyl beta-D-thiogalactopyranoside (IPTG)-regulated expression, and the fused protein was purified using GSH (glutathione) affinity chromatography. ELISA (enzyme-linked immunosorbent assay) was employed to determine the phosphorylation kinase activity of the GST-fused v-Src. This strategy seems to be more promising than the insect cell system or other eukaryotic systems employed in earlier Src expression.

Beta-1,4-galactosyltransferase (beta4Gal-T) (EC 2.4.1.38) plays a multifunctional role in many aspects of normal cell physiology. By now, several dozens of beta4Gal-T genes have been cloned, separated from mouse, chick, bovine, human, etc. This paper presents the cloning and GST-fused expression of mouse beta4Gal-T gene in Escherichia coli (E. coli). The target gene was cloned by PCR, followed by identification by DNA sequencing and expression in E.coli with isopropyl-beta-D-thiogalactoside (IPTG) gradient concentrations, products of which were separated on SDS-PAGE showing that the target protein had the same molecular weight as that of mouse beta4Gal-T. The transcriptional product of beta4Gal-T gene was proved by Western hybridization analysis to be due to GST-fusion.