Phosphorylation of HPr by the bifunctional HPr Kinase/P-ser-HPr phosphatase from Lactobacillus casei controls catabolite repression and inducer exclusion but not inducer expulsion.
We have cloned and sequenced the Lactobacillus casei hprK gene encoding the bifunctional enzyme HPr kinase/P-Ser-HPr phosphatase (HprK/P). Purified recombinant L. casei HprK/P catalyzes the ATP-dependent phosphorylation of HPr, a phosphocarrier protein of the phosphoenolpyruvate:carbohydrate phosphotransferase system at the regulatory Ser-46 as well as the dephosphorylation of seryl-phosphorylated HPr (P-Ser-HPr). The two opposing activities of HprK/P were regulated by fructose-1,6-bisphosphate, which stimulated HPr phosphorylation, and by inorganic phosphate, which stimulated the P-Ser-HPr phosphatase activity. A mutant producing truncated HprK/P was found to be devoid of both HPr kinase and P-Ser-HPr phosphatase activities. When hprK was inactivated, carbon catabolite repression of N-acetylglucosaminidase disappeared, and the lag phase observed during diauxic growth of the wild-type strain on media containing glucose plus either lactose or maltose was strongly diminished. In addition, inducer exclusion exerted by the presence of glucose on maltose transport in the wild-type strain was abolished in the hprK mutant. However, inducer expulsion of methyl beta-D-thiogalactoside triggered by rapidly metabolizable carbon sources was still operative in ptsH mutants altered at Ser-46 of HPr and the hprK mutant, suggesting that, in contrast to the model proposed for inducer expulsion in gram-positive bacteria, P-Ser-HPr might not be involved in this regulatory process.
Dossonnet
V
V
Laboratoire de Génétique des Microorganismes, 78850 Thiverval-Grignon, France.
Monedero
V
V
Zagorec
M
M
Galinier
A
A
Pérez-Martínez
G
G
Deutscher
J
J
D000118:Acetylglucosaminidase / Q000378:metabolism; D001426:Bacterial Proteins; D001483:Base Sequence; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D007780:Lacticaseibacillus casei / Q000201:enzymology* / Q000235:genetics; D008320:Maltose / Q000378:metabolism; D008756:Methylgalactosides / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010710:Phosphates / Q000378:metabolism; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000378:metabolism*; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism; D020218:Response Elements; D013862:Thiogalactosides / Q000378:metabolism; D014166:Transferases / Q000235:genetics
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D008756:Methylgalactosides; D010710:Phosphates; D012097:Repressor Proteins; D013862:Thiogalactosides; C069286:catabolite control proteins, bacteria; C009468:thiomethylgalactoside; D008320:Maltose; D014166:Transferases; C042308:phosphatidylglycerol glyceryl transferase; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C030182:phosphocarrier protein HPr; C110847:HPr kinase; D017346:Protein Serine-Threonine Kinases; C110846:YvoE protein, Bacillus substilis; D010749:Phosphoprotein Phosphatases; D000118:Acetylglucosaminidase; D005947:Glucose