title: Promoter-like mutation affecting HPr and enzyme I of the phosphoenolpyruvate: sugar phosphotransferase system in Salmonella typhimurium.
abstract: A promoter-like mutation, ptsP160, has been identified which drastically reduces expression of the genes specifying two proteins, HPr and enzyme I, of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) in Salmonella typhimurium. This mutation lies between trzA, a gene specifying susceptibility to 1,2,4-triazole, and ptsH, the structural gene for HPr. It leads to a loss of active transport of those sugars that require the PTS for entry into the cell. Pseudorevertants of strains carrying this promoter-like mutation have additional lesions very closely linked to ptsP160 by transduction analysis and are noninducible for HPr and enzyme I above a basal level. Presumably, strains carrying ptsP160 are defective in the normal induction mechanism for HPr and enzyme I, and the pseudorevertants derived from them result from second-site initiation signals within or near this promoter-like element. The induction of HPr and enzyme I above their noninduced levels apparently is not required for transport of at least one PTS sugar, methyl alpha-d-glucopyranoside, since this sugar is taken up by the pseudorevertants at the same rate as by the wild type. The existence of a promoter-like element governing the coordinate inducibility of both HPr and enzyme I suggests that ptsH and ptsI constitute an operon. Wild-type levels of a sugar-specific PTS protein, factor III, are synthesized in response to the crr(+) gene in both a ptsP160 strain and its pseudorevertants; this suggests that the crr(+) gene has its own promoter distinct from ptsP.
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis*; D002250:Carbon Radioisotopes; D002874:Chromosome Mapping; D004352:Drug Resistance, Microbial; D004790:Enzyme Induction; D005632:Fructose / Q000378:metabolism; D005796:Genes; D006027:Glycosides / Q000378:metabolism; D007773:Lactates / Q000378:metabolism; D009097:Multienzyme Complexes / Q000096:biosynthesis*; D009154:Mutation; D009876:Operon; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases / Q000096:biosynthesis*; D011995:Recombination, Genetic; D012486:Salmonella typhimurium / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D014161:Transduction, Genetic; D014230:Triazoles / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D002250:Carbon Radioisotopes; D006027:Glycosides; D007773:Lactates; D009097:Multienzyme Complexes; D014230:Triazoles; D005632:Fructose; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases