Primary Structure of Protein S13 from the Small Subunitof Escherichia coliRibosomes

Abstract

The experimental details which led to the determination of the complete primary structure of protein S13 from the small subunit of E. coli ribosomes are presented. S13 consists of 117 amino acid residues and has the following composition: Asp6, Asn2, Thr6, Ser6, Glu6, Gln2, Pro4, Gly11, Ala11, Cys1, Val7, Met2, Ile12, Leu9, Tyr2, Phe1, His3, Lys11 and Arg15. Tryptophan was not found. The MW of protein S13 is 12,970. The amino acid sequence of the protein was determined by combining the results obtained from liquid phase Edman degradation of the intact protein with those from the peptides isolated after enzymatic digestions with trypsin [EC 3.4.21.4], Staphylococcus aureus protease and thermolysin [EC 3.4.24.4]. Additional information about the primary structure was derived from analysis of the chymotryptic [EC 3.4.21.1] peptides of protein S13 and from its digestion with carboxypeptidase C [EC 3.4.12.1]. The amino acid sequence of protein S13 was compared with the published sequences of the other ribosomal proteins of E. coli and predictions for the secondary structure of this protein were made.