Faculty of Technology, Tokyo University of Agriculture and Technology.
Brenner(Natare. 334, 528 (1988)), analyzing their DNA sequences, proposed that serine proteases originate from a common ancester of cystein protease that existed billions of years ago. In the present study, we are going to discuss this problem in terms of 3 dimensional structures of proteases. Although similarities of amino acid sequences among 11 chymotrypsin family proteases are largely reduced, those in beta-barrel parts are well conserved relative to those in alpha-helices and coil parts. Molecular mechanics calculation of residue-residue interactions in beta-barrel parts indicated that specific inter-residue interactions stabilize beta-barrel structures in serine proteases. The pattern of inter-residue interactions in N-terminal beta-barrel parts is found to be appreciably different from that in C-terminal beta-barrel parts.