C-terminal DNA binding stimulates N-terminal phosphorylation of the outer membrane protein regulator OmpR from Escherichia coli

Sharla K. Ames, Nanja Frankema, Linda Kenney

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76 Scopus citations


Expression of the porin genes of Escherichia coli is regulated in part by the osmolarity of the growth medium. The process is controlled by the histidine kinase EnvZ and the response regulator OmpR. We have previously shown that phosphorylation of OmpR increases its affinity for the upstream regulatory regions of ompF and ompC. We now report that, in the presence of DNA, there is a dramatic stimulation in the level of phospho-OmpR. This effect is independent of the source of phosphorylation, i.e., stimulation of phosphorylation is observed with a small phosphorylating agent such as acetyl phosphate or with protein-catalyzed phosphorylation by the kinase EnvZ. The dephosphorylation rate of phospho-OmpR is affected only slightly by the presence of DNA; thus, the increased level is largely caused by an increased rate of phosphorylation. Stimulation of phosphorylation requires specific binding of DNA by OmpR. Occupancy of the DNA binding domain exposes a trypsin cleavage site in the linker, which connects the phosphorylation domain with the DNA binding domain. Our results indicate that when DNA binds in the C terminus, it enhances phosphorylation in the N terminus, and the linker undergoes a conformational change. A generalized mechanism involving a four- state model for response regulators is proposed.

Original languageEnglish (US)
Pages (from-to)11792-11797
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number21
StatePublished - Oct 12 1999
Externally publishedYes



  • Porin regulation
  • Response regulator
  • Transcriptional activator
  • Two- component regulatory system
  • Winged helix-turn-helix

ASJC Scopus subject areas

  • General

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