Engagement of Arginine Finger to ATP Triggers Large Conformational Changes in NtrC1 AAA+ ATPase for Remodeling Bacterial RNA Polymerase

SummaryThe NtrC-like AAA+ ATPases control virulence and other important bacterial activities through delivering mechanical work to σ54-RNA polymerase to activate transcription from σ54-dependent genes. We report the first crystal structure for such an ATPase, NtrC1 of Aquifex aeolicus, in which the catalytic arginine engages the γ-phosphate of ATP. Comparing the new structure with those previously known for apo and ADP-bound states supports a rigid-body displacement model that is consistent with large-scale conformational changes observed by low-resolution methods. First, the arginine finger induces rigid-body roll, extending surface loops above the plane of the ATPase ring to bind σ54. Second, ATP hydrolysis permits Pi release and retraction of the arginine with a reversed roll, remodeling σ54-RNAP. This model provides a fresh perspective on how ATPase subunits interact within the ring-ensemble to promote transcription, directing attention to structural changes on the arginine-finger side of an ATP-bound interface.

Graphical AbstractFigure optionsDownload high-quality image (268 K)Download as PowerPoint slideHighlights
► Crystal structure of NtrC1C,E239A shows the engaged state of the arginine finger
► Conformational changes propagate from arginine finger to distant σ54-binding loops
► ATP binding at the interface affects both subunits forming the active site
► Resulting model: ATP directs rigid-body displacement to perform work on RNAP