Transcription regulation of ompF and ompC by a single transcription factor, OmpR.
The ompF and ompC genes of Escherichia coli are reciprocally regulated by a single transcription factor, phosphorylated OmpR (OmpR-P), depending upon medium osmolarity. This regulation involves activation of ompF and its repression with concomitant activation of ompC. This occurs through OmpR-P binding to four (F1, F2, F3, and F4) and three (C1, C2, and C3) sites located upstream of the ompF and ompC promoters, respectively, through a novel mechanism. Here we show that there is a distinct OmpR-P binding hierarchy within F1, F2, and F3 sites as well as within C1, C2, and C3 sites. Each of these sites contains two tandem 10-bp OmpR-P-binding subsites, a-site and b-site (from 5' to 3' direction). OmpR-P has higher affinity to the downstream b-site than to the upstream a-site in each case. Six OmpR-P molecules bind to F and C sites two-by-two in a discontinuous "galloping" manner. We propose that this tight hierarchical binding of a transcription factor, OmpR, allows distinct stepwise regulation of ompF and ompC transcription, which minimizes their overlapping expression upon changes in the medium osmolarity to achieve the reciprocal expression of ompF and ompC.
Yoshida
Takeshi
T
Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
Qin
Ling
L
Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
Egger
Linda A
LA
Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854.
Inouye
Masayori
M
Department of Biochemistry, Robert Wood Johnson Medical School, Piscataway, New Jersey 08854. Electronic address: inouye@rwja.umdnj.edu.
D001426:Bacterial Proteins / Q000737:chemistry*; D001483:Base Sequence; D001665:Binding Sites; D004247:DNA / Q000737:chemistry; D003850:Deoxyribonuclease I / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D008954:Models, Biological; D008969:Molecular Sequence Data; D018272:Porins / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012689:Sequence Homology, Nucleic Acid; D015534:Trans-Activators / Q000737:chemistry*; D014158:Transcription, Genetic
D001426:Bacterial Proteins; C113724:OmpC protein; C109237:OmpF protein; D018272:Porins; D015534:Trans-Activators; C112177:osmolarity response regulator proteins; D004247:DNA; D003850:Deoxyribonuclease I