A novel protein kinase that controls carbon catabolite repression in bacteria

HPr(Ser) kinase is the sensor in a multicomponent phosphorelay system that controls catabolite repression, sugar transport and carbon metabolism in Gram‐positive bacteria. Unlike most other protein kinases, it recognizes the tertiary structure in its target protein, HPr, a phosphocarrier protein of the bacterial phosphotransferase system and a transcriptional cofactor controlling the phenomenon of catabolite repression. We have identified the gene (ptsK) encoding this serine/threonine protein kinase and characterized the purified protein product. Orthologues of PtsK have been identified only in bacteria. These proteins constitute a novel family unrelated to other previously characterized protein phosphorylating enzymes. The Bacillus subtilis kinase is shown to be allosterically activated by metabolites such as fructose 1,6‐bisphosphate and inhibited by inorganic phosphate. In contrast to wild‐type B. subtilis, the ptsK mutant is insensitive to transcriptional regulation by catabolite repression. The reported results advance our understanding of phosphorylation‐dependent carbon control mechanisms in Gram‐positive bacteria.