PRIMARY STRUCTURE OF BASE NONSPECIFIC AND ACID RIBONUCLEASE FROM BULLFROG (RANA-CATESBEIANA)

A base non-specific acid ribonuclease (RNase RCL2) was purified from b ullfrog liver [H. Yagi et al. Bioi. Pharm. Ball., 18, 219-222 (1992)]. The sequence study and comparison of the amino acid sequence of the e nzyme with homologous RNases from oyster, drosophila and chicken liver suggested that the RNase RCL2 consisted of two components, large prot ein fraction (182 amino acid residues) and peptide 2 (20 amino acid re sidues) or peptide 1 (18 amino acid residues), and that both component s bind with disulfide bridge. The RNase preparation was probably forme d from a single polypeptide protein by processing with some proteases. The amino acid sequence of RNase RCL2 showed that the RNase belongs t o the RNase of RNase T-2 family and its sequence most resembles chicke n liver acid RNase. Tn RNase RCL2, the amino acid residues which consi st of the active site and major base recognition site of RNase Rh, a t ypical RNase of RNase T-2 family, are very,yell conserved except for T yr57 (RNase Rh numbering), and part of the amino acid residues of the minor base recognition site (Phe101 and Pro92) are also conserved.