A New Type of Peptide Subunit in the Murein of Arthrobacter Strain J39

The murein (peptidoglycan) of Arthrobacter strain J39 was found to contain D-alanine, L-lysine, glycine, and D-and L-glutamic acid in the molar ratio of 1:1:3:2. Approximately half of the D-glutamic acid was hydroxylated. The UDP-activated precursors of the murein were isolated. The molar ratios Mur:Gly:Glu = 1:1:2 and MunGly:Glu: Ala = 1:1:2:2 were found for the tripeptide and the penta-peptide, respectively. Partial acid hydrolysis of the purified precursors and analysis of the obtained peptides proved the sequence N-acetylmuramylglycyl-γ-D-glutamyl-L-glutamic acid for the UDP-Ar-acetylmuramyl tripeptide, and the sequence n-acetylmuramylglycyl-γ-D-glutamyl-L-glutamyl-D-alanyl-D-alanine for the UDP-iV-acetylmuramylpentapeptide. Analysis of the peptides isolated from partial acid hydrolysates of cell walls confirmed the amino acid sequence of the peptide subunit as found in the murein precursors. The cross-linkage of the peptide subunits was shown to be performed by the peptide glycylglycyl-L-lysine. The TV-terminal glycine is attached to the a-carboxyl group of the D-glutamic acid, while the e-amino group of the lysine is bound to the D-alanine of the adjacent peptide subunit.