Isolation and biochemical characterization of rubelase, a non-hemorrhagic elastase from Crotalus ruber ruber (Red Rattlesnake) venom.

A novel non-hemorrhagic basic metalloprotease, rubelase, was isolated from the venom of Crotalus ruber ruber. Rubelase hydrolyzes succinyl-L-alanyl-L-alanyl-L-alanyl p-nitroanilide (STANA), a specific substrate for elastase, and the hydrolytic activity was inhibited by chelating agents. It also hydrolyzes collagen and fibrinogen. However, hemorrhagic activity was not observed. By ESI/Q-TOF and MALDI/TOF mass spectrometry combined with Edman sequencing procedure, the molecular mass of rubelase was determined to be 23,266 Da. Although its primary structure was similar to rubelysin (HT-2), a hemorrhagic metalloprotease isolated from the same snake venom, the circumstances surrounding putative zinc binding domain HEXXHXXGXXH were found to be different when the three-dimensional computer models of both metalloproteases were compared. The cytotoxic effects of rubelase and rubelysin on cultured endothelial and smooth muscle cells were also different, indicating that the substitution of several amino acid residues causes the changes of active-site conformation and cell preference.