50-S Ribsomal Proteins. Peptide Studies on Two Acidic Proteins, A1 and A2, Isolated from 50-S Ribosomes of Escherichia coli

Abstract

Peptide studies on two acidic proteins, A1 and A2, from 50-S ribosomes of Escherichia coli indicate a closely related primary structure. 1 Amino acid compositions of the tryptic peptides of the two proteins are identical, with exception of the amino terminal peptide. 2 The N-terminal amino acid sequence of A2-protein is Ser-Ile-Thr-Lys, while that of A1-protein is N-acetyl-Ser-Ile-Thr-Lys. 3 The estimated number of 120 amino acid residues in each polypeptide chain is consistent with the physical molecular weight estimate. 4 In 50% of the polpeptide chains, in both A1 or A2-protein, a specific lysine residue is replaced by ɛ-N-monomethyl-lysine.