Role of the Extracytoplasmic Function Protein Family Sigma Factor RpoE in Metal Resistance of Escherichia coli

Abstract

RpoE of Escherichia coli is a sigma factor of the extracytoplasmic function protein family and is required for the expression of proteins involved in maintaining the integrity of periplasmic and outer membrane components. RpoE of E. coli was needed for full resistance to Zn(II), Cd(II), and Cu(II). Promoter gene fusion and quantitative real time reverse transcription (RT)-PCR (qRT-PCR) assays demonstrated that expression of RpoE was induced by metals. Global gene expression profiles upon metal treatment of a ⌬rpoE mutant strain and its wild-type strain were analyzed with microarrays, and selected genes were confirmed by qRT-PCR. The absolute number of genes that were changed in their expression upon metal stress was similar in both strains, but the increase or decrease in transcript levels upon metal treatment was smaller in the ⌬rpoE mutant strain than in the wild type. Genes showing increased expression in the ⌬rpoE mutant strain encoded proteins that belong to general defense systems against protein-denaturing agents. Genes showing decreased expression were part of the RpoE modulon itself plus the ompC gene, encoding a major outer membrane protein. A ⌬ompC deletion strain was as sensitive to Cu(II) and Cd(II) as the ⌬rpoE mutant or a ⌬rpoE ⌬ompC double mutant strain. In the case of Zn(II), the double mutant was more sensitive than either single mutant. This indicates that increased expression of OmpC contributes to the RpoE modulon-mediated response to metals.

Periplasmic proteins encoded by VCA0261–0260 and VC2216 genes together with copA and cueR products are required for copper tolerance but not for virulence in Vibrio cholerae

“…Since there is increasing evidence to indicate that the periplasm is an important cellular compartment for copper homeostasis (Bagai et al, 2008;Egler et al, 2005;Hiniker et al, 2005;Macomber et al, 2007), elucidating the involvement of VcCot (VCA0261-0260) and Vc-CopG (VC2216) homologues in V. cholerae copper tolerance represented an interesting topic of study. The evaluation of the role of VC2215 and VC0974 genes in copper resistance was also interesting, since their original annotations were only based on sequence similarity.…”

Characterization of Copper-Inducible Promoters Regulated by CpxA/CpxR inEscherichia coli

“…26,27) Recently, DNA microarray assays have shown that zinc also stimulates the expression of genes among CpxAR regulon. 22,28,29) After a number of comparison of the sensitivity of the wild type and the cpxAR mutant to several metals, LiCl, NaCl, MgCl 2 , KCl, CaCl 2 , CrCl 3 , MnCl 2 , FeCl 2 , CoCl 2 , NiCl 2 , CuCl 2 , ZnCl 2 , RbCl, SrCl, CsCl, BaCl 2 , PbCl 4 , and AgNO 3 , we found that the sensitivity of the cpxRA-null mutant was For S1 nuclease analysis using these probes, the expected size of protected fragments (or transcripts) are: 81-nt for cpxP probe-1; 195-nt for ftnB probe-2; 147-nt for htrA probe-3; 170-nt for ppiA probe-4; 122-nt for spy probe-5; 148-nt (p1) and 234-nt (p2) for ybaJ probe-6; 90-nt for yccA probe-7; 119-nt for ycfS probe-8; 93-nt for ydeH probe-9; 180-nt for yebE probe-10; 160-nt for yihE probe-11; 109-nt for yobB probe-12; 133-nt for yqjA probe-13. highest against copper, followed by zinc (data not shown).…”

Escherichia coli heat-shock proteins IbpA/B are involved in resistance to oxidative stress induced by copper

“…Both pathways respond to environmental stresses and control expression of genes required for repairing of damaged proteins in the envelope (DiGiuseppe & Silhavy, 2003). Recently, it was found that activity of the disulfide isomerase DsbC (Hiniker et al, 2005) and increased expression of the porin OmpC (Egler et al, 2005) are required for copper tolerance. DsbC rearranges non-native disulfide bonds formed in periplasmic proteins damaged by copper; the underlying mechanism of OmpC function remains unclear.…”

“…During anaerobic growth, copper toxicity increases and another efflux system encoded by the cusCFBA operon is necessary for full copper tolerance (Grass & Rensing, 2001;Outten et al, 2001;Silver & Phung, 2005). In the presence of high copper concentrations, when the efflux complexes are overloaded, E. coli cells activate general stress responses governed by the sigma factor RpoE (Egler et al, 2005) and the twocomponent signal transduction system CpxRA (Kershaw et al, 2005;Yamamoto & Ishihama, 2005). Both pathways respond to environmental stresses and control expression of genes required for repairing of damaged proteins in the envelope (DiGiuseppe & Silhavy, 2003).…”