Disease relevance of envZ

• Isolation of mutations in the alpha operon of Escherichia coli that suppress the transcriptional defect conferred by a mutation in the porin regulatory gene envZ [1].
• Moreover, the deletion strains did not exhibit the pleiotropic membrane protein deficiency observed with certain envZ mutants [2].
• Molecular analysis of the two-component genes, ompR and envZ, in the symbiotic bacterium Xenorhabdus nematophilus [3].
• The two-component regulatory system ompR-envZ controls the virulence of Shigella flexneri [4].
• Although the order of the ompR and envZ genes of V. cholerae is similar to that of the ompB operon of E. coli, S. typhimurium and X. nematophilus, the Vibrio operon exhibits a number of novel features [5].

High impact information on envZ

• The envZ mutant, termed envZ30, was isolated as a pseudorevertant, which phenotypically suppresses an ompR3-type mutant exhibiting an OmpF- OmpC-constitutive phenotype [6].
• Osmoregulation of gene expression. II. DNA sequence of the envZ gene of the ompB operon of Escherichia coli and characterization of its gene product [7].
• During our search of numerous bacteria we found that the symbiotic/pathogenic bacterium Xenorhabdus nematophilus contained the operon encoding both ompR and envZ [3].
• Further genetic analysis established that heterologous phosphorylation between EnvZX.n. and OmpR of E. coli (OmpRE.c.) accounted for the complementation of the delta envZ strain [3].
• The behavior of these mutants in haploid, and in diploid with other envZ alleles, is consistent with a model in which EnvZ mediates osmoregulation by controlling the concentration of a single species [8].

Biological context of envZ

• Previously isolated mutations in envZ exhibit an OmpF- OmpC+ phenotype and also have pleiotropic effects on other exported proteins [9].
• The sequence data also showed that ompR and envZ form an operon, where the coding regions overlap by four base-pairs [10].
• Analysis of ompR frameshift mutations showed that translation of envZ is almost totally dependent on the translation of the upstream gene ompR [10].
• These results indicate the involvement of a factor(s) besides the ompR and envZ gene products in the osmoregulation of OmpF production [11].
• Isolation and characterization of chain-terminating nonsense mutations in a porin regulator gene, envZ [12].

Anatomical context of envZ

• In Shigella flexneri, the ompB locus (containing the ompR and envZ genes) was found to modulate expression of the vir genes, which are responsible for invasion of epithelial cells. vir gene expression was markedly enhanced under conditions of high osmolarity (300 mosM), similar to that encountered in tissues both extra- and intracellularly [4].
• Secretion of haemolysin into the periplasm is independent of perA (envZ) and in fact, mutants in perA (envZ) harbouring pPM431 show hyperproduction of periplasmic haemolysin [13].

Associations of envZ with chemical compounds

• 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 [14].
• Our results indicate that while methionine or glutamine replacements could cause similar effects on OmpF and OmpC expression, they conferred different abilities on the mutant proteins to be suppressed by envZ [15].

Regulatory relationships of envZ

• These results provide evidence that envZ function influences the DNA-binding activity of OmpR and suggest that high-affinity binding of OmpR to the upstream sequences of ompF is correlated with the repression of OmpF production [16].

Other interactions of envZ

• DNA-binding properties of the transcription activator (OmpR) for the upstream sequences of ompF in Escherichia coli are altered by envZ mutations and medium osmolarity [16].
• When this method was used to clone two chromosomal mutations in the envZ gene of Escherichia coli, a locus which encodes a membrane-bound sensory protein involved in the osmoregulation of outer membrane porin biosynthesis, more than 50% of the retransformants from the plasmids selected by size were found to exhibit the mutant phenotype [17].

Analytical, diagnostic and therapeutic context of envZ

• The identity of the envZ gene product was confirmed by immunoprecipitation [18].
• The order of genes on the chromosome inferred from restriction mapping, was (74 min)...pckA envZ ompR...(75 min) [19].
• To further analyze the role of the conserved sequence, envZ of Escherichia coli was subjected to random PCR mutagenesis and mutant alleles that produced a high-osmolarity phenotype, in which ompF was repressed, were isolated [20].

References