In vivo phosphorylation of OmpR, the transcription activator of the ompF and ompC genes in Escherichia coli.

An in vivo approach was taken to assess whether the phosphorylated state of the transcription activator OmpR was affected by changes in the osmolarity of the growth medium or by mutations in envZ, the gene encoding the inner membrane histidine kinase that phosphorylates OmpR. We present results that support the view that increased phosphorylation of OmpR is correlated with enhanced expression of ompC. The in vivo phosphorylation approach was also used to show that OmpR can be phosphorylated in an envZ null strain. This result indicates that phosphorylation cross talk can occur in vivo between OmpR and a kinase(s) that is functionally homologous to envZ.