LOSS OF PROTEIN KINASE-CATALYZED PHOSPHORYLATION OF HPR, A PHOSPHOCARRIER PROTEIN OF THE PHOSPHOTRANSFERASE SYSTEM, BY MUTATION OF THE PTSHGENE CONFERS CATABOLITE REPRESSION RESISTANCE TO SEVERAL CATABOLIC GENES OF BACILLUS-SUBTILIS

In gram-positive bacteria, HPr, a phosphocarrier protein of the phosph oenolpyruvate:sugar phosphotransferase system (PTS), is phosphorylated by an ATP-dependent, metabolite-activated protein kinase on seryl res idue 46. In a Bacillus subtilis mutant strain in which Ser-46 of HPr w as replaced with a nonphosphorylatable alanyl residue (ptsH1 mutation) , synthesis of gluconate kinase, glucitol dehydrogenase, mannitol-1-P dehydrogenase and the mannitol-specific PTS permease was completely re lieved from repression by glucose, fructose, or mannitol, whereas synt hesis of inositol dehydrogenase was partially relieved from catabolite repression and synthesis of alpha-glucosidase and glycerol kinase was still subject to catabolite repression. When the S46A mutation in HPr was reverted to give S46 wild-type HPr, expression of gluconate kinas e and glucitol dehydrogenase regained full sensitivity to repression b y PTS sugars. These results suggest that phosphorylation of HPr at Ser -46 is directly or indirectly involved in catabolite repression. A str ain deleted for the ptsGHI genes was transformed with plasmids express ing either the wild-type ptsH gene or various S46 mutant ptsH genes (S 46A or S46D). Expression of the gene encoding S46D HPr, having a struc ture similar to that of P-ser-HPr according to nuclear magnetic resona nce data, caused significant reduction of gluconate kinase activity, w hereas expression of the genes encoding uild-type or S46A HPr had no e ffect on this enzyme activity. When the promoterless lacZ gene was put under the control of the gut promoter and was subsequently incorporat ed into the amyE gene on the B. subtilis chromosome, expression of bet a-galactosidase was inducible by gluconate and repressed by glucose. H owever, we observed no repression of beta-galactosidase activity in a strain carrying the ptsH1 mutation. Additionally, we investigated a cc pA mutant strain and observed that all of the enzymes which we found t o be relieved from carbon catabolite repression in the ptsH1 mutant st rain were also insensitive to catabolite repression in the ccpA mutant . Enzymes that were repressed in the ptsH1 mutant were also repressed in the ccpA mutant.