A HISTIDINE PROTEIN-KINASE IS INVOLVED IN POLAR ORGANELLE DEVELOPMENT IN CAULOBACTER-CRESCENTUS

Mutations having pleiotropic effects on polar organelle development (pod) in Caulobacter crescentus have been identified and shown to occur in at least 13 genes scattered throughout the genome. Mutations at each locus affect a unique combination of polar traits, suggesting that complex interactions occur among these genes. The DNA sequence of one of these genes, pleC, indicates that it is homologous to members of the family of histidine protein kinase genes. Members of this family include the sensor components of the bacterial two-component regulatory systems. Furthermore, in vitro experiments demonstrated that the PleC protein was capable of autophosphorylation. These results suggest that the PleC protein (and perhaps the proteins encoded by the other pod genes as well) regulates the expression of genes involved in polar organelle development through the phosphorylation of key regulatory proteins. The use of a phosphorelay system cued to internal changes in the cell would provide a mechanism for coordinating major changes in gene expression with the completion of specific cell cycle events.