Resumen de Crystal Structure of Escherichia coli σE with the Cytoplasmic Domain of Its Anti-σ RseA

Jonathan L. Tupy, Elizabeth A. Campbell, Tanja M. Gruber

• The σ factors are the key regulators of bacterial transcription. ECF (extracytoplasmic function) σ's are the largest and most divergent group of σ70 family members. ECF σ's are normally sequestered in an inactive complex by their specific anti-σ factor, which often spans the inner membrane. Here, we determined the 2 Å resolution crystal structure of the Escherichia coli ECF σ factor σE in an inhibitory complex with the cytoplasmic domain of its anti-σ, RseA. Despite extensive sequence variability, the two major domains of σE are virtually identical in structure to the corresponding domains of other σ70 family members. In combination with a model of the σE holoenzyme and biochemical data, the structure reveals that RseA functions by sterically occluding the two primary binding determinants on σE for core RNA polymerase.