title: Isolation of temperature-sensitive mutations in murC of Staphylococcus aureus.
abstract: Enzymes in the bacterial peptidoglycan biosynthesis pathway are important targets for novel antibiotics. Of 750 temperature-sensitive (TS) mutants of Gram-positive Staphylococcus aureus, six were complemented by the murC gene, which encodes the UDP-N-acetylmuramic acid:l-alanine ligase. Each mutation resulted in a single amino acid substitution and, in all cases, the TS phenotype was suppressed by high osmotic stress. In mutant strains with the G222E substitution, a decrease in the viable cell number immediately after shift to the restrictive temperature was observed. These results suggest that S. aureus MurC protein is essential for cell growth. The MurC H343Y mutation is located in the putative alanine recognition pocket. Consistent with this, allele-specific suppression was observed of the H343Y mutation by multiple copies of the aapA gene, which encodes an alanine transporter. The results suggest an in vivo role for the H343 residue of S. aureus MurC protein in high-affinity binding to L-alanine.
authors.affiliation: Graduate School of Pharmaceutical Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
authors.forename: Mihoko
authors.initials: M
authors.lastname: Ishibashi
authors.forename: Kenji
authors.initials: K
authors.lastname: Kurokawa
authors.forename: Satoshi
authors.initials: S
authors.lastname: Nishida
authors.forename: Kohji
authors.initials: K
authors.lastname: Ueno
authors.forename: Miki
authors.initials: M
authors.lastname: Matsuo
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Sekimizu
mesh_terms: D015964:Gene Expression Regulation, Bacterial; D018698:Glutamic Acid / Q000235:genetics; D005998:Glycine / Q000235:genetics; D009154:Mutation; D010453:Peptide Synthases / Q000235:genetics* / Q000378:metabolism; D013211:Staphylococcus aureus / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification*; D013696:Temperature; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000378:metabolism
chemical_list: D014538:Uridine Diphosphate N-Acetylmuramic Acid; D018698:Glutamic Acid; D010453:Peptide Synthases; C023229:UDP-N-acetylmuramoyl-alanine synthetase; D005998:Glycine