Effect of D-amino acids on structure and synthesis of peptidoglycan in Escherichia coli.
Growth of Escherichia coli in the presence of certain D-amino acids, such as D-methionine, results in the incorporation of the D-amino acid into macromolecular peptidoglycan and can be lethal at high concentrations. Previous studies suggested that incorporation was independent of the normal biosynthetic pathway. An enzymatic reaction between the D-amino acid and macromolecular peptidoglycan was proposed as the mechanism of incorporation. The application of more advanced analytical techniques, notably high-pressure liquid chromatography, revealed that the presence of a D-amino acid susceptible to incorporation induced a multiplicity of alterations in peptidoglycan metabolism. Results derived basically from the study of samples treated with D-Met, D-Trp, and D-Phe indicated that the incorporation of a D-amino acid results in the accumulation of two major new muropeptides whose general structures most likely are GlucNAc-MurNAc-L-Ala-D-Glu-m-diaminopimelic acid-D-aa and GlucNAc-MurNAc-L-Ala-D-Glu-m-diaminopimelic acid-D-Ala-GlucNAc-MurNAc-L-Ala-D-Glu-m-diaminopimelic acid-D-aa, where D-aa represents a residue of the added D-amino acid. Resting cells are proficient in the incorporation of D-amino acids and can reach peptidoglycan modification levels comparable to those in growing cells. Under our conditions, D-amino acids had no apparent effect on growth or morphology but caused a severe inhibition of peptidoglycan synthesis and cross-linking, possibly leading to a reduction in the amount of peptidoglycan per cell. The properties of the reaction support the involvement of a penicillin-insensitive LD-transpeptidase enzyme in the synthesis of modified muropeptides and a possible inhibitory action of D-amino acids on high-molecular-weight penicillin-binding proteins.
Caparrós
M
M
Centro de Biología Molecular, Facultad de Ciencias, Consejo Superior de Investigaciones Científicas-Universidad Autónoma de Madrid, Spain.
Pisabarro
A G
AG
de Pedro
M A
MA
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000494:pharmacology*; D000667:Ampicillin / Q000494:pharmacology; D004926:Escherichia coli / Q000254:growth & development / Q000378:metabolism*; D006020:Glycopeptides / Q000378:metabolism; D008969:Molecular Sequence Data; D010457:Peptidoglycan / Q000096:biosynthesis*; D010458:Peptidyl Transferases / Q000378:metabolism*; D013237:Stereoisomerism
D000596:Amino Acids; D006020:Glycopeptides; D010457:Peptidoglycan; D000667:Ampicillin; D010458:Peptidyl Transferases