title: Temperature-sensitive mutant of Escherichia coli K-12 with an impaired D-alanine:D-alanine ligase.
abstract: The temperature-sensitive Escherichia coli mutant strain ST-640 lyses at the restrictive temperature except when an osmotic stabilizer or a high concentration of d-alanine is present. The presence of dl-alanyl-dl-alanine does not prevent lysis. The rate of murein synthesis, followed in a wall medium, is decreased at both 30 and 42 C. d-Alanyl-d-alanine and uridine diphosphate-N-acetyl-muramyl (UDP-MurNAc)-pentapeptide are synthesized in decreased amounts, accompanied by accumulation of UDP-MurNAc-tripeptide at 42 C but not at 30 C. Uridine nucleotide precursors leak into the medium, especially out of the mutant cells. This leakage is prevented when NaCl is present. The d-alanine: d-alanine ligase (ADP) (EC 6.3.2.4) of the mutant strain, assayed in crude extracts, is temperature sensitive. The impaired ligase is relatively resistant to d-cycloserine and other inhibitors of the enzyme. Combined genetic and enzymatic results show that the low ligase activity is due to a mutation in the ddl gene, the structural gene for d-alanine: d-alanine ligase.
mesh_terms: D000409:Alanine / Q000378:metabolism; D000591:Amino Acid Isomerases / Q000378:metabolism; D002247:Carbon Isotopes; D002474:Cell-Free System; D003470:Culture Media; D003523:Cycloserine / Q000494:pharmacology; D004151:Dipeptides / Q000378:metabolism / Q000494:pharmacology; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development; D005796:Genes; D005998:Glycine / Q000494:pharmacology; D009154:Mutation; D009842:Oligopeptides / Q000096:biosynthesis; D009997:Osmotic Pressure; D010453:Peptide Synthases / Q000378:metabolism*; D010457:Peptidoglycan / Q000096:biosynthesis; D011995:Recombination, Genetic; D012965:Sodium Chloride; D013237:Stereoisomerism; D013395:Sucrose; D013696:Temperature; D014316:Tritium
chemical_list: D002247:Carbon Isotopes; D003470:Culture Media; D004151:Dipeptides; D009842:Oligopeptides; D010457:Peptidoglycan; D014316:Tritium; D012965:Sodium Chloride; D013395:Sucrose; D003523:Cycloserine; D000591:Amino Acid Isomerases; D010453:Peptide Synthases; D000409:Alanine; D005998:Glycine