Phosphotransfer functions mutated Bacillus subtilis HPr-like protein Crh carrying a histidine in the active site.

The Bacillus subtilis protein Crh exhibits strong similarity to HPr, a phosphocarrier protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). HPr phosphorylated at His-15 can transfer its phosphoryl group to several EIIAs of the PTS for sugar transport and phosphorylation. In addition, it phosphorylates and activates transcriptional regulators containing PTS regulation domains (PRDs). In Gram-positive bacteria, it also controls the enzyme glycerol kinase. Since in Crh the active site His-15 of HPr is replaced with a glutamine, Crh was not able to carry out the catalytic and regulatory functions mediated by P approximately His-HPr. However, when Gln-15 of Crh was replaced with a histidine, Crh gained most of the catalytic and regulatory functions exerted by HPr. To allow CrhQ15H to efficiently phosphorylate and activate the PRD-containing antiterminator LicT, which controls the expression of the bgIS gene and the bgIPH operon, it was sufficient to express the crhQ15H allele under control of the spac promoter in monocopy. By contrast, to phosphorylate and activate glycerol kinase and to allow a ptsH deletion strain (devoid of HPr) to slowly grow on the non-PTS substrate glycerol and to efficiently utilize the PTS sugars glucose and mannitol, the crhQ15H allele had to be expressed from a multicopy plasmid.