Pseudomonas aeruginosa SutA wedges RNAP lobe domain open to facilitate promoter DNA unwinding

SutA is a transcription factor which increases transcription activity of an RNA polymerase (RNAP). Here, authors present cryo-EM structures of SutA-bound RNAP-sigma(S) holoenzyme and SutA-bound transcription initiation complex, which reveals SutA wedging the RNAP-beta lobe open to aid unwinding. Pseudomonas aeruginosa (Pae) SutA adapts bacteria to hypoxia and nutrition-limited environment during chronic infection by increasing transcription activity of an RNA polymerase (RNAP) holoenzyme comprising the stress-responsive sigma factor sigma(S) (RNAP-sigma(S)). SutA shows no homology to previously characterized RNAP-binding proteins. The structure and mode of action of SutA remain unclear. Here we determined cryo-EM structures of Pae RNAP-sigma(S) holoenzyme, Pae RNAP-sigma(S) holoenzyme complexed with SutA, and Pae RNAP-sigma(S) transcription initiation complex comprising SutA. The structures show SutA pinches RNAP-beta protrusion and facilitates promoter unwinding by wedging RNAP-beta lobe open. Our results demonstrate that SutA clears an energetic barrier to facilitate promoter unwinding of RNAP-sigma(S) holoenzyme.

Automated summary

This study investigates the mechanism of SutA's action on RNAP. Cryo-EM structures reveal how SutA assists RNAP in unwinding the promoter DNA. These findings are significant for understanding the function of SutA and the transcription regulation mechanism during bacterial infection.