Full antitumor action of recombinant seminal ribonuclease depends on the removal of its N-terminal methionine

Bovine seminal RNase (BS-RNase) is a dimeric member of the pancreatic-like ribonuclease superfamily, with antitumor activity. We have reported that recombinant Met(-1) BS-RNase is a less potent cytotoxic factor, while structurally and catalitically indistinguishable from BS-RNase isolated from natural sources. Mature recombinant BS-RNase instead displays full antitumor action. This suggests that the conformation of the N-terminal region of BS-RNase is among the structural determinants of its antitumor action, in addition to its catalytic activity and its quaternary structure.