The role of ω‐subunit of Escherichia coli RNA polymerase in stress response

In this study, we have performed UV cross‐linking experiments using 32P azido‐labeled ppGpp to probe its association with RNAP in the absence and presence of ω, and observed weaker binding of ppGpp to the RNAP without ω. Furthermore, we followed the binding kinetics of ppGpp to RNAP with and without ω by isothermal titration calorimetry and found it to be concurrent with the cross‐linking results. Native ω is intrinsically disordered, and we have used a previously characterized structured mutant of ω, which affects the plasticity of the active site of RNAP. Results show that the flexibility conferred by the unstructured ω is a prerequisite for ppGpp binding to RNAP. We have analyzed the stress‐associated phenotypes in an E. coli strain devoid of ω (∆rpoZ). ppGpp levels in ∆rpoZ strain were found to be similar to that of the wild‐type strain. Interestingly, when the ∆rpoZ strain of E. coli was transferred after nutritional stress to an enriched media, the recovery of growth was compromised. We have identified a new phenotype of ∆rpoZ strain corresponding to defect in biofilm formation in minimal media. Omega subunit of RNAP is essential for ppGpp‐mediated stress response in Escherichia coli. We observed the first novel phenotype in bacterial cells devoid of omega subunit that is their inability to form biofilm in minimal media.
Source: Genes to Cells - Category: Genetics & Stem Cells Authors: Tags: ORIGINAL ARTICLE Source Type: research