title: The reaction of bovine pancreatic ribonuclease A with 6-chloropurineriboside 5'-monophosphate. Evidence on the existence of a phosphate-binding sub-site.
abstract: The chemical modification of bovine pancreatic ribonuclease A by 6-chloropurine 9-beta-D-ribofuranosyl 5'-monophosphate was studied under several reaction conditions. The reaction, at pH 7.3, 40 degrees C and a nucleotide: enzyme molar ratio of 60, showed a high degree of specificity in comparison to those corresponding to the base or the nucleoside. The main derivative was isolated by means of CM-cellulose chromatography. Subtilisin cleavage of this derivative showed that the substitution had taken place in the S-peptide moiety. Tryptic digestion of the S-peptide indicated that a lysine residue had been modified. Enzymatic and physico-chemical considerations showed that the actual site of reaction was the alpha-amino group of Lys-1. The structural and kinetic properties of the derivative are consistent with the existence of a phosphate-binding sub-site near the N-terminal region of the enzyme.
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000818:Animals; D001665:Binding Sites; D002417:Cattle; D004720:Endonucleases / Q000378:metabolism*; D007291:Inosine Monophosphate / Q000031:analogs & derivatives*; D008968:Molecular Conformation; D010179:Pancreas / Q000201:enzymology*; D010446:Peptide Fragments / Q000032:analysis; D010710:Phosphates / Q000378:metabolism*; D011685:Purine Nucleotides / Q000378:metabolism*; D012259:Ribonuclease, Pancreatic; D012260:Ribonucleases / Q000378:metabolism*; D013381:Subtilisins; D014357:Trypsin
chemical_list: D000596:Amino Acids; D010446:Peptide Fragments; D010710:Phosphates; D011685:Purine Nucleotides; D007291:Inosine Monophosphate; C018488:6-chloropurine 9-beta-D-ribofuranosyl 5'-monophosphate; D004720:Endonucleases; D012260:Ribonucleases; D012259:Ribonuclease, Pancreatic; D013381:Subtilisins; D014357:Trypsin