ST14 is one of the type II transmembrane serine proteases that correlates with the process of tumor metastasis. The C-terminal catalytic region (900 bp) of ST14 was cloned into the expression vector pGEX-4T-2 and the positive plasmid pGEX-4T-2-ST14 was transformed into E. coli BL21, then cultured and induced with IPTG. The chaperonin GroEL was found to be tightly associated with the fusion protein and co-purified with it by regular GST affinity chromatography. A method for the removal of contaminating GroEL from GST-ST14 fusion protein was described, the purity of product was 96.2%. Enzyme activity assay indicated that this fusion protein had serine protease activity.
