PRIMARY STRUCTURE OF PORCINE SPLEEN RIBONUCLEASE - SEQUENCE HOMOLOGY

The primary structure of porcine spleen RNase (RNase Psp1) was investi gated as a mean of assessing the structure-function relationship of ba se non-specific ribonucleases of animal origin. N-terminal analysis of RNase Psp1 yielded three N-terminal sequences. These peptides were se parated by gel-filtration on Superdex 75HR, after reduction and S-carb oxymethylation of RNase Psp1. Determination of the amino-acid sequence of these peptides indicated that the RNase Psp1 preparation consisted of three peptides having 20 (RCM RNase Psp1 pep1), 15 (RCM RNase Psp1 pep2), and 164 (RCM RNase Psp1 pro) amino-acid residues, respectively . It possessed two unique segments containing most of the active site amino-acid residues of the RNases of the RNase T2 family. The alignmen t of these three peptides in RNase Psp1 was determined by comparison w ith the other enzymes in the RNase T2 family. The overall results show ed that RCM RNase Psp1 pep1 and RCM RNase Psp1 pep2 are derived from t he N-terminal and C-terminal regions of RNase Psp1, respectively, prob ably by processing by some protease. The molecular mass of the protein moiety of RNase Psp1 was 23235 Da.