A NOVEL GENE THAT INTERFERES WITH THE PHOSPHOTRANSFER SIGNAL-TRANSDUCTION MEDIATED BY THE ENVZ OSMOSENSOR IN ESCHERICHIA-COLI

In Escherichia coli, expression of the major outer membrane proteins, OmpC and OmpF, is regulated in response to the medium osmolarity and o ther environmental stimuli, A two-component signal transduction system , mediated by EnvZ and OmpR, is crucially responsible for this osmotic regulation of the ompC and ompF genes, In this study, an E. coli gene was cloned, which interferes with expression of both the ompC and omp F genes at the level of transcription, provided that the cloned gene w as introduced in E. coli cells by a multicopy plasmid, The gene produc t was identified as F107, which was previously characterized as a hypo thetical protein in E. coli genome databases, F107 containing 107 amin o acids appears to be highly hydrophobic, and has a sequence similarit y to the eukaryotic type of cytochrome-e oxidase subunit III, The mech anism by which F107 inhibits transcription of ompC and ompF was examin ed extensively, mainly by using a set of envZ and ompR mutants, These results suggested that F107 interferes specifically with a function of the EnvZ osmosensory kinase, Possible mechanisms by which F107 affect the EnvZ function are discussed.