Abstract
The widely distributed bacterial σ54‐dependent transcription regulates pathogenicity and numerous adaptive responses in diverse bacteria. Formation of the σ54‐dependent open promoter complex is a multi‐step process driven by AAA+ ATPases. Non‐hydrolysable nucleotide analogues are particularly suitable for studying such complexity by capturing various intermediate states along the energy coupling pathway. Here we report a novel ATP analogue, ADP–MgF3−, which traps an AAA+ ATPase with its target σ54. The MgF3−‐dependent complex is highly homogeneous and functional assays suggest it may represent an early transcription intermediate state valuable for structural studies.