Hideaki Watanabe

Identification of the Glutamyl and Histidyl Residues Involved in the Active Site of a Minor Ribonuclease from Aspergillus saitoi

A glutamyl and two histidyl residues that are suspected to be part of the active site of a base non-specific, guanine-preferential ribonuclease from Aspergillus saitoi (RNase Ms) were located.RNase Ms modified by radioactive iodoacetate was digested by α-chymotrypsin, then separated by paper chromatography and paper electrophoresis. The amino acid composition of the radioactive peptide indicated that the site of the modification was Glu57.A simple procedure to separate three histidyl-residue-containing peptides from RNase Ms was established. The procedure was used on the photooxidized RNase Ms, and the photooxidized histidyl residues were found to be His39 and His91.