The ompB Operon Partially Determines Differential Expression of OmpC in Salmonella typhi and Escherichia coli (original) (raw)
Related papers
Journal of bacteriology, 1999
Expression of the Escherichia coli OmpC and OmpF outer membrane proteins is regulated by the osmolarity of the culture media. In contrast, expression of OmpC in Salmonella typhi is not influenced by osmolarity, while OmpF is regulated as in E. coli. To better understand the lack of osmoregulation of OmpC expression in S. typhi, we compared the expression of the ompC gene in S. typhi and E. coli, using ompC-lacZ fusions and outer membrane protein (OMP) electrophoretic profiles. S. typhi ompC expression levels in S. typhi were similar at low and high osmolarity along the growth curve, whereas osmoregulation of E. coli ompC in E. coli was observed during the exponential phase. Both genes were highly expressed at high and low osmolarity when present in S. typhi, while expression of both was regulated by osmolarity in E. coli. Complementation experiments with either the S. typhi or E. coli ompB operon in an S. typhi DeltaompB strain carrying the ompC-lacZ fusions showed that both S. typh...
Journal of Bacteriology
Expression of the Escherichia coli OmpC and OmpF outer membrane proteins is regulated by the osmolarity of the culture media. In contrast, expression of OmpC in Salmonella typhi is not influenced by osmolarity, while OmpF is regulated as in E. coli. To better understand the lack of osmoregulation of OmpC expression in S. typhi, we compared the expression of the ompC gene in S. typhi and E. coli, using ompC-lacZ fusions and outer membrane protein (OMP) electrophoretic profiles. S. typhi ompC expression levels in S. typhi were similar at low and high osmolarity along the growth curve, whereas osmoregulation of E. coli ompC in E. coli was observed during the exponential phase. Both genes were highly expressed at high and low osmolarity when present in S. typhi, while expression of both was regulated by osmolarity in E. coli. Complementation experiments with either the S. typhi or E. coli ompB operon in an S. typhi ⌬ompB strain carrying the ompC-lacZ fusions showed that both S. typhi and E. coli ompC were not regulated by osmolarity when they were under the control of S. typhi ompB. Interestingly, in the same strain, both genes were osmoregulated under E. coli ompB. Surprisingly, in E. coli ⌬ompB, they were both osmoregulated under S. typhi or E. coli ompB. Thus, the lack of osmoregulation of OmpC expression in S. typhi is determined in part by the ompB operon, as well as by other unknown transacting elements present in S. typhi.
Proceedings of the National Academy of Sciences, 1989
EnvZ and OmpR, the regulatory proteins for ompF and ompC expression in Escherichia coli, belong to a modulator-effector family of regulatory proteins which are essential for the response to environmental signals. We show that the soluble cytoplasmic domain of the transmembrane modulator protein EnvZ is phosphorylated in vitro by [7-32P]-ATP. We also demonstrate that the phosphate group can, in turn, be transferred to the transcription activator protein OmpR. The pH stability properties of the phosphate groups linked to EnvZ indicate that this molecule contains histidyl phosphate. The invariant His-243 of EnvZ corresponds to the phosphorylated His-48 of the chemotactic modulator protein CheA. Substitution of His-243 with valine produces an EnvZ that is refractory to phosphorylation and can no longer catalyze the transfer of phosphate to OmpR. Furthermore, in a AenvZ strain of E. coli, containing the envZ Val-243 plasmid, ompC expression is elevated 7-fold relative to that found in cells carrying the wild-type envZ plasmid. Based on these results we propose a model in which the phosphorylated state of OmpR modulates the expression of the ompF and ompC genes.
Molecular Microbiology, 1991
OmpC, a major outer-membrane protein, is highly expressed when Salmonella typhi is grown in nutrient broth (NB) of either low (NB + 0% sucrose) or high (NB + 20% sucrose) osmolarity. This contrasts with the expression of Escherichia coti OmpC, which is inhibited in low osmolarity and enhanced in high osmolarity, as has been described previously (van Alphen and Lugtenberg, 1977;. Nevertheless, expression of S. typhi OmpC is dependent on the £. coli OmpR transcriptional activator. These findings suggest differences between the mechanisms of osmoregulation of gene expression in both bacteria, although common effectors appear to be shared.
Journal of Biological Chemistry, 1991
The transcriptional factors, OmpR and EnvZ, are crucially involved in the osmotic regulation of o m p F and o m p C expression in Escherichia coli. The DNA binding ability of the positive regulator, OmpR, is modulated through its phosphorylation and dephosphorylation mediated by EnvZ in response to the medium osmolarity. In this study, two examples of a novel type of mutant o m p R allele, ompR96A and ompR115S, whose phenotype is OmpF-OmpC-irrespective of the medium osmolarity, were characterized. These mutations result in amino acid conversions, G~u~~ to Ala and Arg''' to Ser, respectively, within the phosphorylation domain of OmpR. Nevertheless, these mutant proteins were capable of undergoing phosphorylation and dephosphorylation normally, just like wild-type OmpR. However, the phosphorylation-dependent enhancement of their in vitro DNA binding ability was found to be severely affected. It was thus revealed that these mutant OmpR represent a novel type in terms of the mechanism of phosphorylation-dependent activation of the function of OmpR, i.e. those are normally phosphorylated but not activated to bind to the cognate promoter DNAs. In this respect, it was further suggested that OmpR oligomerization may be involved in the mechanism underlying the phosphorylation-dependent enhancement of the DNA binding ability of OmpR. The mutant proteins characterized in this study seem to be defective in this particular oligomerization process observed in vitro. Expression of the Escherichia coli outer membrane proteins, OmpF and OmpC, is regulated in response to the medium osmolarity. The transcriptional factors, OmpR and EnvZ, are crucially involved in the osmotic regulation of ompF and ompC expression, namely OmpR is the actual activator, which binds to both the ompF and ompC promoter DNAs, and EnvZ is a transmembrane osmotic sensor, which exhibits both OmpR phosphorylation and dephosphorylation abilities (see Refs. 1-4 for reviews). Recently, it was revealed that phosphotransfer between these two regulatory components, originally observed i n vitro, appears to play a crucial role in signal transduction and the consequent osmotic regulation i n vivo (see Refs. 3 and 4 for review). In this respect, we previously addressed the main question of what the biochemical consequence of OmpR phosphorylation is and demonstrated i n vitro that the phos-* This work was supported by grants from the Ministry of Education, Science and Culture of Japan.
Molecular analysis of OmpR binding sequences involved in the regulation of ompF in Escherichia coli
FEMS Microbiology Letters, 1995
OmpR, the transcriptional regulatory protein of ompF, had not been previously shown to specifically bind to the-70 to-60-bp region of ompF. We show that the-102 to-76-bp sequence of ompF has a high affinity binding site for OmpR and produced a single OmpR/ompF complex (complex b). Extension of this DNA fragment to include an inverted repeat sequence located between the-71 and-6Cbp region resulted in the formation of a second, slower migrating complex (complex a). A-102 to-58-bp fragment containing a substitution of the-70 CG bp was able to form complex b, but not complex a. A mutant OmpR protein derived from a strain that can not repress ompF was unable to form complex a, while complex b was formed normally. Deletion of the-70 CG bp resulted in incomplete repression of OmpF. These results suggest that OmpR binds to the-71 to-64-bp region and that this sequence plays a role in the regulation of ompF in Escherichia coli.
MicC, a Second Small-RNA Regulator of Omp Protein Expression in Escherichia coli
Journal of Bacteriology, 2004
In a previous bioinformatics-based search for novel small-RNA genes encoded by the Escherichia coli genome, we identified a region, IS063, located between the ompN and ydbK genes, that encodes an ϳ100nucleotide small-RNA transcript. Here we show that the expression of this small RNA is increased at a low temperature and in minimal medium. Twenty-two nucleotides at the 5 end of this transcript have the potential to form base pairs with the leader sequence of the mRNA encoding the outer membrane protein OmpC. The deletion of IS063 increased the expression of an ompC-luc translational fusion 1.5-to 2-fold, and a 10-fold overexpression of the small RNA led to a 2-to 3-fold repression of the fusion. Deletion and overexpression of the IS063 RNA also resulted in increases and decreases, respectively, in OmpC protein levels. Taken together, these results suggest that IS063 is a regulator of OmpC expression; thus, the small RNA has been renamed MicC. The antisense regulation was further demonstrated by the finding that micC mutations were suppressed by compensatory mutations in the ompC mRNA. MicC was also shown to inhibit ribosome binding to the ompC mRNA leader in vitro and to require the Hfq RNA chaperone for its function. We suggest that the MicF and MicC RNAs act in conjunction with the EnvZ-OmpR two-component system to control the OmpF/OmpC protein ratio in response to a variety of environmental stimuli.