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Journal of Bacteriology, May 2000, p. 2582-2590, Vol. 182, No. 9
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.

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

Valérie Dossonnet,1 Vicente Monedero,1 Monique Zagorec,2 Anne Galinier,3 Gaspar Pérez-Martínez,4 and Josef Deutscher1,*

Laboratoire de Génétique des Microorganismes, 78850 Thiverval-Grignon,1 Laboratoire de Recherche sur la Viande, 78352 Jouy-en-Josas,2 and Institut de Biologie et Chimie des Protéines, 69367 Lyon,3 France, and Departamento de Biotecnología, Instituto de Agroquímica y Tecnología de Alimentos, 46100 Burjasot, Valencia, Spain4

Received 23 November 1999/Accepted 9 February 2000

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.

* Corresponding author. Mailing address: Laboratoire de Génétique des Microorganismes, INRA-CNRS URA 1925, F-78850 Thiverval-Grignon, France. Phone: 33-1-30815447. Fax: 33-1-30815457. E-mail: jdeu{at}platon.grignon.inra.fr.

Journal of Bacteriology, May 2000, p. 2582-2590, Vol. 182, No. 9
0021-9193/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.


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