Streptococci and lactococci synthesize large amounts of HPr(Ser-P)(His~P).
HPr is a protein of the phosphoenolpyruvate:sugar phosphotransferase transport system (PTS). In gram-positive bacteria, HPr can be phosphorylated on Ser-46 by the kinase/phosphorylase HprK/P and on His-15 by phospho-enzyme I (EI~P) of the PTS. In vitro studies with purified HPrs from Bacillus subtilis, Enterococcus faecalis, and Streptococcus salivarius have indicated that the phosphorylation of one residue impedes the phosphorylation of the other. However, a recent study showed that while the rate of Streptococcus salivarius HPr phosphorylation by EI~P is reduced at acidic pH, the phosphorylation of HPr(Ser-P) by EI~P, generating HPr(Ser-P)(His~P), is stimulated. This suggests that HPr(Ser-P)(His~P) synthesis may occur in acidogenic bacteria unable to maintain their intracellular pH near neutrality. Consistent with this hypothesis, significant amounts of HPr(Ser-P)(His~P) have been detected in some streptococci. The present study was aimed at determining whether the capacity to synthesize HPr(Ser-P)(His~P) is common to streptococcal species, as well as to lactococci, which are also unable to maintain their intracellular pH near neutrality in response to a decrease in extracellular pH. Our results indicated that unlike Staphylococcus aureus, B. subtilis, and E. faecalis, all the streptococcal and lactococcal species tested were able to synthesize large amounts of HPr(Ser-P)(His~P) during growth. We also showed that Streptococcus salivarius IIABLMan, a protein involved in sugar transport by the PTS, could be efficiently phosphorylated by HPr(Ser-P)(His~P).
Roy
Denis J
DJ
Groupe de Recherche en Ecologie buccale, Faculte de medecine dentaire, Universite Laval, 2420 rue de la Terrasse, Quebec City, QC G1V0A6, Canada.
Casabon
Israël
I
Vaillancourt
Katy
K
Huot
Jonathan L
JL
Vadeboncoeur
Christian
C
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006639:Histidine / Q000378:metabolism; D017045:Lactococcus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006005:Phosphorylases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000378:metabolism; D013291:Streptococcus / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D012694:Serine; D006639:Histidine; D006005:Phosphorylases; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System