A Novel Gene That Interferes with the Phosphotransfer Signal Transduction Mediated by the EnvZ Osmosensor inEscherichia coli

摘要

InEscherichia coli, expression of the major outer membrane proteins, OmpC and OmpF, is regulated in response to the medium osmolarity and other environmental stimuli. A two-component signal transduction system, mediated by EnvZ and OmpR, is crucially responsible for this osmotic regulation of theompCandompFgenes. In this study, anE. coligene was cloned, which interferes with expression of both theompCandompFgenes at the level of transcription, provided that the cloned gene was introduced inE. colicells by a multicopy plasmid. The gene product was identified as F107, which was previously characterized as a hypothetical protein inE. coligenome databases. F107 containing 107 amino acids appears to be highly hydrophobic, and has a sequence similarity to the eukaryotic type of cytochrome-coxidase subunit III. The mechanism by which F107 inhibits transcription ofompCandompFwas examined extensively, mainly by using a set ofenvZandompRmutants. 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.