Two genes, MGFc (40) and MGFc (24), encoding different E peptides of mechano-growth factor (MGF), were obtained by a four-step PCR strategy and subcloned into pRSETC and pGEX-6p-1. Recombinant MGFc(40) protein (4 mg l(-1)) was expressed and purified by affinity chromatography using His60 Ni Superflow. Recombinant MGFc(24) protein was purified using a glutathione-Sepharose 4B column. After enzymatic cleavage of the GST-tail, 1 mg MGFc(24) protein l(-1) was obtained. MGFc(40) and MGFc(24), which are involved in proliferation and differentiation, stimulated cell proliferation and inhibited cell differentiation of C2C12 cells.