title: Functional characterization of the incomplete phosphotransferase system (PTS) of the intracellular pathogen Brucella melitensis.
abstract: BACKGROUND
  In many bacteria, the phosphotransferase system (PTS) is a key player in the regulation of the assimilation of alternative carbon sources notably through catabolic repression. The intracellular pathogens Brucella spp. possess four PTS proteins (EINtr, NPr, EIIANtr and an EIIA of the mannose family) but no PTS permease suggesting that this PTS might serve only regulatory functions.
  
  
  RESULTS
  In vitro biochemical analyses and in vivo detection of two forms of EIIANtr (phosphorylated or not) established that the four PTS proteins of Brucella melitensis form a functional phosphorelay. Moreover, in vitro the protein kinase HprK/P phosphorylates NPr on a conserved serine residue, providing an additional level of regulation to the B. melitensis PTS. This kinase activity was inhibited by inorganic phosphate and stimulated by fructose-1,6 bisphosphate. The genes encoding HprK/P, an EIIAMan-like protein and NPr are clustered in a locus conserved among α-proteobacteria and also contain the genes for the crucial two-component system BvrR-BvrS. RT-PCR revealed a transcriptional link between these genes suggesting an interaction between PTS and BvrR-BvrS. Mutations leading to the inactivation of EINtr or NPr significantly lowered the synthesis of VirB proteins, which form a type IV secretion system. These two mutants also exhibit a small colony phenotype on solid media. Finally, interaction partners of PTS proteins were identified using a yeast two hybrid screen against the whole B. melitensis ORFeome. Both NPr and HprK/P were shown to interact with an inorganic pyrophosphatase and the EIIAMan-like protein with the E1 component (SucA) of 2-oxoglutarate dehydrogenase.
  
  
  CONCLUSIONS
  The B. melitensis can transfer the phosphoryl group from PEP to the EIIAs and a link between the PTS and the virulence of this organism could be established. Based on the protein interaction data a preliminary model is proposed in which this regulatory PTS coordinates also C and N metabolism.
authors.affiliation: Research Unit in Molecular Biology (URBM), University of Namur, Namur, Belgium.
authors.forename: Marie
authors.initials: M
authors.lastname: Dozot
authors.forename: Sandrine
authors.initials: S
authors.lastname: Poncet
authors.forename: Cécile
authors.initials: C
authors.lastname: Nicolas
authors.forename: Richard
authors.initials: R
authors.lastname: Copin
authors.forename: Houda
authors.initials: H
authors.lastname: Bouraoui
authors.forename: Alain
authors.initials: A
authors.lastname: Mazé
authors.forename: Josef
authors.initials: J
authors.lastname: Deutscher
authors.forename: Xavier
authors.initials: X
authors.lastname: De Bolle
authors.forename: Jean-Jacques
authors.initials: JJ
authors.lastname: Letesson
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D017347:Brucella melitensis / Q000201:enzymology* / Q000235:genetics / Q000472:pathogenicity; D002006:Brucellosis / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D010766:Phosphorylation; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D014774:Virulence
chemical_list: D001426:Bacterial Proteins; D010770:Phosphotransferases