Characterization of the RcsC -> YojN -> RcsB phosphorelay signaling pathway involved in capsular synthesis in Escherichia coli

Escherichia coli and other enteric microorganisms produce an extracellular polysaccharide capsule, called colanic acid, under certain environmental co nditions. This capsular synthesis is regulated by the RcsC (sensor kinase) --> YojN (phosphotransfer intermediate) --> RcsB (response regulator) phosp horelay signal transduction under certain growth conditions. Nonetheless, l ittle is known about signals that exaggerate the Res-system. To gain insigh t into signals that activate the Rcs-system, here we searched for genes tha t activate the Rcs-system, provided that those on a multicopy plasmid were introduced into E. coli. We identified several such genes, namely, rcsB, rc sA, djlA, lolA, and ompG. The DjlA, LolA, and OmpG proteins are particularl y interesting in that they are all located on the cell surface, where the p rimary sensor RcsC histidine-kinase is localized. Implications of these fin dings are discussed with special reference to the mechanism by which RcsC p erceives external signals.