NEW-PROTEIN KINASE AND PROTEIN PHOSPHATASE FAMILIES MEDIATE SIGNAL-TRANSDUCTION IN BACTERIAL CATABOLITE REPRESSION

Carbon catabolite repression (CCR) is the prototype of a signal transd uction mechanism, In enteric bacteria, cAMP was considered to be the s econd messenger in CCR by playing a role reminiscent of its actions in eukaryotic cells, However, recent results suggest that CCR in Escheri chia coli is mediated mainly by an inducer exclusion mechanism, In man y Gram-positive bacteria, CCR is triggered by fructose-1,6-bisphosphat e, which activates HPr kinase, presumed to be one of the most ancient serine protein kinases, We here report cloning of the Bacillus subtili s hprK and hprP genes and characterization of the encoded HPr kinase a nd P-Ser-H:Pr phosphatase, P-Ser-HPr phosphatase forms a new family of phosphatases together with bacterial phosphoglycolate phosphatase, ye ast glycerol-3-phosphatase, and 2-deoxyglucose-6-phosphate phosphatase whereas HPr kinase represents a new family of protein kinases on its own. It does not contain the domain structure typical for eukaryotic p rotein kinases. Although up to now the HPr modifying/demodifying enzym es were thought to exist only in Gram-positive bacteria, a sequence co mparison revealed that they also are present in several Gram-negative pathogenic bacteria.