Three-dimensional Structures and Molecular Evolution of Ribonucleases

Abstract

The crystal structures of six microbial ribonucleases have been determined. Among these enzymes, homology in both the three-dimensional structure and amino acid sequence is present in the C-terminal half of the polypeptide chain, which is folded as a three-stranded, anti-parallel β-sheet containing the catalytic residues. This fact is consistent with the idea of a diverging family of enzymes.