Open AccessTHE MECHANISM OF ACTION OF RIBONUCLEASE
Author(s) -
Gordon C. K. Roberts,
Edward A. Dennis,
Donella H. Meadows,
Jack S. Cohen,
Oleg Jardetzky
Publication year - 1969
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.62.4.1151
Subject(s) - pseudorotation , chemistry , stereochemistry , active site , mechanism of action , protonation , residue (chemistry) , binding site , bovine pancreatic ribonuclease , histidine , crystallography , ribonuclease , enzyme , biochemistry , organic chemistry , rna , molecule , ion , in vitro , gene
The possible mechanisms of action of bovine pancreatic ribonuclease are discussed in the light of the detailed knowledge of the geometry of the active site that has been derived from studies of inhibitor binding by X-ray diffraction and nuclear magnetic resonance. When combined with a knowledge of the mechanism of phosphate ester hydrolysis, this information imposes severe geometric constraints on possible mechanisms of action of the enzyme. Two types of mechanism can be distinguished, the linear and the pseudorotation. The linear mechanism includes a catalytic role for both histidine residues at the active site and does not involve pseudorotation of the intermediate. In contrast, in the pseudorotation mechanism one histidine residue performs all the catalytic functions, while the other serves only to bind the phosphate anion; this necessarily involves pseudorotation of the intermediate and specific protonation of the leaving group by the enzyme. The mode of binding of the product of the reaction, cytidine-3′-monophosphate, has been elucidated by X-ray diffraction and nuclear magnetic resonance. If the substrate binds in an analogous way, only the linear mechanism is possible. This mechanism is described in detail.