Elevated levels of VCA0117 (VasH) in response to external signals activate the type VI secretion system of Vibrio cholerae O1 El Tor A1552.

The type VI nanomachine is critical for Vibrio cholerae to establish infections and to thrive in niches co-occupied by competing bacteria. The genes for the type VI structural proteins are encoded in one large and two small auxiliary gene clusters. VCA0117 (VasH) - a σ -transcriptional activator - is strictly required for functionality of the type VI secretion system since it controls production of the structural protein Hcp.

The Y233 gatekeeper of DmpR modulates effector-responsive transcriptional control of σ -RNA polymerase.

DmpR is the obligate transcriptional activator of genes involved in (methyl)phenol catabolism by Pseudomonas putida. DmpR belongs to the AAA class of mechano-transcriptional regulators that employ ATP-hydrolysis to engage and remodel σ -RNA polymerase to allow transcriptional initiation. Previous work has established that binding of phenolic effectors by DmpR is a prerequisite to relieve interdomain repression and allow ATP-binding to trigger transition to its active multimeric conformation, and further that a structured interdomain linker between the effector- and ATP-binding domains is involved in coupling these processes.