The structural basis for the self-inhibition of DNA binding by apo-σ70

Abstract

AbstractInitiation of transcription inEscherichia coliis facilitated by promoter specificity factors, such as σ70, which bind promoter dsDNA when in complex with RNA polymerase (RNAP), in which it is in an extended conformation with solvent-exposed DNA-interacting residues. If so, what in the structure of apo-σ70prevents binding to promoter dsDNA at high affinity? By performing cross-linking mass spectrometry (CL-MS) and integrative structural modelling we elucidate structure models of apo-σ70that exhibit burial of almost all DNA-binding residues.In vivoCL-MS detects crosslinks unique to the compact fold of apo-σ70that occur at stationary growth phase. Conclusively, we provide structural information to show that the high affinity DNA-binding capabilities of apo-σ70are conformationally-inhibited and can be activated mostly in the context of transcription.One-Sentence SummaryThis work provides a structural mechanism for why apo-σ70does not bind promoters at high affinity when it is not in the direct context of transcription.