Structural Comparison of Some Microbial Ribonucleases

Previous comparison of amino acid sequences and three-dimensional structures has shown that the microbial ribonucleases from an evolutionarily related family that is separate from that of the pancreatic ribonucleases (Hill et al., 1983). The microbial and pancreatic ribonucleases catalyse the same two step hydrolysis of RNA via a cyclic 2′3′ intermediate. However, the specificities are different; the microbial enzymes prefer a purine base on the 3′ side of the scissile phosphate, and in some cases are very guanine specific.