title: The HPr(Ser) kinase of Streptococcus salivarius: a hexameric bifunctional enzyme controlled by glycolytic intermediates and inorganic phosphate.
abstract: Phosphorylation of HPr, the small phosphocarrier protein of the phosphoenolpyruvate:sugar phosphotransferase system, on Ser46 by the HPr(Ser) kinase (HPrK/P) is a vital step in catabolite repression in Gram-positive bacteria. Streptococcus salivarius HPrK/P is reported to be a multimeric protein not regulated by metabolic intermediates. We re-evaluated the molecular mass of S. salivarius HPrK/P using sedimentation equilibrium ultracentrifugation, demonstrated that S. salivarius HPrK/P dephosphorylated HPr(Ser-P) and further characterised the effect of fructose 1,6-bisphosphate and other metabolic intermediates on enzyme activities. The molecular mass of S. salivarius HPrK/P was 201305 Da, suggesting that streptococcal HPrK/P was a hexameric protein. Fructose 1,6-bisphosphate poorly activated streptococcal HPrK/P but protected kinase activity against inhibition by inorganic phosphate and inhibited dephosphorylation of HPr(Ser-P). Phosphoenolpyruvate and 2-phosphoglycerate, but not fructose 1-P, fructose 6-P, and ribulose 1,5-bisphosphate, also protected kinase activity against inhibition by inorganic phosphate. Thus, unlike previous reports, we show that fructose 1,6-bisphosphate and other key glycolytic intermediates played a pivotal role as a modulator of streptococcal HPrK/P activities.
authors.affiliation: Département de Biochimie et de Microbiologie, and Faculté de Médecine Dentaire, Université Laval, Québec, QC, Canada G1K 7P4.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Frey
authors.forename: Sylvie
authors.initials: S
authors.lastname: Nessler
authors.forename: Sonia
authors.initials: S
authors.lastname: Fieulaine
authors.forename: Katy
authors.initials: K
authors.lastname: Vaillancourt
authors.forename: Michel
authors.initials: M
authors.lastname: Frenette
authors.forename: Christian
authors.initials: C
authors.lastname: Vadeboncoeur
mesh_terms: D001426:Bacterial Proteins; D005635:Fructosediphosphates / Q000378:metabolism*; D005988:Glyceric Acids / Q000378:metabolism; D006019:Glycolysis; D008970:Molecular Weight; D010710:Phosphates / Q000378:metabolism*; D010728:Phosphoenolpyruvate / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D010770:Phosphotransferases / Q000737:chemistry / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013291:Streptococcus / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D005635:Fructosediphosphates; D005988:Glyceric Acids; D010710:Phosphates; C008885:2-phosphoglycerate; D010728:Phosphoenolpyruvate; D010770:Phosphotransferases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr; C029063:fructose-1,6-diphosphate