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 report here that recombinant Met(-1) BS-RNase is a less potent cytotoxic factor, while structurally and catalytically 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. (C) 1995 Academic Press, Inc.