Bovine pancreatic ribonuclease: fifty years of the first enzymatic reaction mechanism.

Fifty years ago, the group of Tony Mathias and Bob Rabin at University College London deduced the first mechanism for catalysis by an enzyme, ribonuclease [Findlay, D., Herries, D. G., Mathias, A. P., Rabin, B. R., and Ross, C. A. (1961) Nature 190, 781-784]. Here, we celebrate this historic accomplishment by surveying knowledge of enzymology and protein science at that time, facts that led to the formulation of the mechanism, criticisms and alternative mechanisms, data that supported the proposed mechanism, and some of the refinements that have since provided a more precise picture of catalysis of RNA cleavage by ribonucleases. The Mathias and Rabin mechanism has appeared in numerous textbooks, monographs, and reviews and continues to have a profound impact on biochemistry.

Back to the future: ribonuclease A.

Pancreatic ribonuclease A (EC 3.1.27.5, RNase) is, perhaps, the best-studied enzyme of the 20th century. It was isolated by René Dubos, crystallized by Moses Kunitz, sequenced by Stanford Moore and William Stein, and synthesized in the laboratory of Bruce Merrifield, all at the Rockefeller Institute/University. It has proven to be an excellent model system for many different types of experiments, both as an enzyme and as a well-characterized protein for biophysical studies. Of major significance was the demonstration by Chris Anfinsen at NIH that the primary sequence of RNase encoded the three-dimensional structure of the enzyme. Many other prominent protein chemists/enzymologists have utilized RNase as a dominant theme in their research. In this review, the history of RNase and its offspring, RNase S (S-protein/S-peptide), will be considered, especially the work in the Merrifield group, as a preface to preliminary data and proposed experiments addressing topics of current interest. These include entropy-enthalpy compensation, entropy of ligand binding, the impact of protein modification on thermal stability, and the role of protein dynamics in enzyme action. In continuing to use RNase as a prototypical enzyme, we stand on the shoulders of the giants of protein chemistry to survey the future.