Specificity of pancreatic ribonuclease-A. An X-ray study of a protein-nucleotide complex.
The modified purine nucleotide 8-oxo-guanosine-2'-phosphate binds at the pyrimidine binding site of ribonuclease-A. The O8-2'GMP inhibitor is in a syn conformation, with an intramolecular hydrogen bond between the N-3 atom of the base and the O-5' atom of the ribose. The essential groups of the protein involved in base recognition are O gamma 45 and N-45, which form hydrogen bonds to the five-membered ring of the heterocyclic base. Mobility of enzyme side-chains (viz. Lys41, Lys66, His119) close to the catalytic cleft of the protein allows conformational flexibility in the substrate binding region of ribonuclease-A. Inhibitor binding alters the solvent structure of the protein but the overall shape of the enzyme is not effected.
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D006150:Guanine Nucleotides; D006157:Guanosine Monophosphate / Q000031:analogs & derivatives; D046911:Macromolecular Substances; D008968:Molecular Conformation; D010179:Pancreas / Q000201:enzymology; D011487:Protein Conformation; D012259:Ribonuclease, Pancreatic / Q000037:antagonists & inhibitors; D014961:X-Ray Diffraction
D006150:Guanine Nucleotides; D046911:Macromolecular Substances; D006157:Guanosine Monophosphate; C039543:8-oxoguanosine 2'-phosphate; D012259:Ribonuclease, Pancreatic