NH2-Terminal Amino Acid Distribution and Amino Acid Composition of Streptococcus faecalis R Soluble and Ribosomal Proteins

摘要

The NH2-terminal amino acid distribution of Streptococcus faecalis R soluble and ribosomal proteins isolated from cells at different stages of growth on either folate-sufficient or folate-deficient medium was determined by the dinitrophenyl method. The NH2-terminal residues do not follow the random distribution observed for the total amino acid composition of S. faecalis soluble and ribosomal proteins. Methionine and alanine occur most frequently; serine, threonine, aspartic and glutamic acids, and glycine are also present at the NH2-terminal position of S. faecalis R proteins. The absence of folic acid yields cells that are incapable of formylating methionyl-transfer ribonucelic acid tRNAf^Met, but does not affect either the qualitative or quantitative NH2-terminal distribution of total soluble or total ribosomal proteins compared to cells grown with folate. A small quantitative difference was observed in the frequency of distribution of certain amino acids at the NH2-termini between log and stationary phase soluble proteins. The amino acid residues found at the NH2-terminal position of S. faecalis proteins are qualitatively similar to those reported for several other organisms.