title: Properties of a Streptococcus salivarius spontaneous mutant in which the methionine at position 48 in the protein HPr has been replaced by a valine.
abstract: HPr is a protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) that participates in the concomitant transport and phosphorylation of sugars in bacteria. In gram-positive bacteria, HPr is also reversibly phosphorylated at a seryl residue at position 46 (Ser-46) by a metabolite-activated ATP-dependent kinase and a Pi-dependent HPr(Ser-P) phosphatase. We report in this article the isolation of a spontaneous mutant (mutant A66) from a streptococcus (Streptococcus salivarius) in which the methionine at position 48 (Met-48) in the protein HPr has been replaced by a valine (Val). The mutation inhibited the phosphorylation of HPr on Ser-46 by the ATP-dependent kinase but did not prevent phosphorylation of HPr by enzyme I or the phosphorylation of enzyme II complexes by HPr(His-P). The results, however, suggested that replacement of Met-48 by Val decreased the affinity of enzyme I for HPr or the affinity of enzyme II proteins for HPr(His-P) or both. Characterization of mutant A66 demonstrated that it has pleiotropic properties, including the lack of IIILman, a specific protein of the mannose PTS; decreased levels of HPr; derepression of some cytoplasmic proteins; reduced growth on PTS as well as on non-PTS sugars; and aberrant growth in medium containing a mixture of sugars.
authors.affiliation: Department of Biochemistry (Sciences) and Faculty of Dentistry, Université Laval, Québec, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Vadeboncoeur
authors.forename: L
authors.initials: L
authors.lastname: Gauthier
authors.forename: G
authors.initials: G
authors.lastname: Gagnon
authors.forename: A
authors.initials: A
authors.lastname: Leduc
authors.forename: D
authors.initials: D
authors.lastname: Brochu
authors.forename: R
authors.initials: R
authors.lastname: Lapointe
authors.forename: B
authors.initials: B
authors.lastname: Desjardins
authors.forename: M
authors.initials: M
authors.lastname: Frenette
mesh_terms: D001426:Bacterial Proteins; D001483:Base Sequence; D004187:Disaccharides / Q000378:metabolism; D006601:Hexoses / Q000378:metabolism; D008715:Methionine / Q000235:genetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics* / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D013291:Streptococcus / Q000235:genetics*; D014633:Valine / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D004187:Disaccharides; D006601:Hexoses; D008715:Methionine; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr; D017346:Protein Serine-Threonine Kinases; D014633:Valine