Gene Construction, Expression and Activities Analysis of Human Leptin
重组人瘦素的基因构建、表达及活性鉴定

Six 89bp primers were designed on the base of the cDNA sequence encoding the human leptin reported on the NCBI. The synthetic gene with 464bp encoding rhLep was obtained by SOE ( splicing by overlap extension) PCR. The expression vector pET22b( )/rhLep was constructed and transformed into E.coli BL21(DE3). The rhLep protein was expressed as inclusion bodies with the yield of more than 50% of total bacterial proteins after IPTG induction. The rhLep protein,which has a molecular weight about 16kD,was purified by Ni 2 affinity chromatography column and identified by SDS-PAGE. The MTT Assay shows that rhLep promotes EC304 cells growth at the low concentration of 10ng/mL to 30 ng/mL,and rhLep appears cytotoxic to EC304 cells with the high dose of 50ng/mL to 225ng/mL. The viability of EC304 cells decreases to 1.2% with the concentration of 225ng/mL of rhLep. The massive apoptosis of rhLep on EC304 cells is observed by AO-staining under fluorescent microscope. All these results would lay the foundation for the further study of its biological functions in vitro and in vivo.