Expression of bovine seminal ribonuclease in Escherichia coli

Bovine seminal RNAase (BS-RNAase), an unusually dimeric member of the pancreatic-like ribonuclease superfamily, is also a multifunctional biological effector, with antitumor, immunosuppressive, and antispermatogenic activities. We report here the cloning of a semi-synthetic cDNA coding for the protein subunit chain, its expression with a T7 expression system in Escherichia coli inclusion bodies, the dimerization of correctly reoxidized monomeric protein, followed by the purification in high yields of the recombinant enzyme, and by its conversion to a protein undistinguishable from BS-RNAase as isolated from seminal vesicles, both in its catalytic activity and in the micro-heterogeneity of its quaternary structure.