title: Characteristic phenotypes associated with ptsN-null mutants in Escherichia coli K-12 are absent in strains with functional ilvG.
abstract: The phosphotransferase system (PTS), encompassing EI, HPr, and assorted EII proteins, uses phosphoenolpyruvate to import and phosphorylate sugars. A paralog of EIIA of the sugar PTS system known as ptsN has been purported to regulate organic nitrogen source utilization in Escherichia coli K-12. Its known biochemical function, however, relates to potassium homeostasis. The evidence for regulation of organic nitrogen source utilization by ptsN is based primarily on the defective growth of ΔptsN mutants on amino acid nitrogen sources and other nutrient combinations. These observations were made with E. coli strains MG1655 and W3110, which carry a nonfunctional version of ilvG. There are three isozymes that effectively catalyze the first committed step of branched-chain amino acid biosynthesis, but ilvG is unique for doing so effectively across a range of potassium concentrations. Here we show that all of the nutrient utilization phenotypes attributed to ptsN are manifested selectively in strains lacking functional ilvG. We conclude that the ptsN gene product does not regulate organic nitrogen source utilization as previously proposed.
authors.affiliation: Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Marshall Louis
authors.initials: ML
authors.lastname: Reaves
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Rabinowitz
mesh_terms: D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism*; D000596:Amino Acids / Q000378:metabolism*; D048168:Escherichia coli K12 / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics; D017353:Gene Deletion; D010641:Phenotype; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000172:deficiency* / Q000235:genetics
chemical_list: D000596:Amino Acids; D029968:Escherichia coli Proteins; D000095:Acetolactate Synthase; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C529959:PtsN protein, E coli