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Snapshot of a Molecular Motor

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Stucture Magazine Cover-Tracy NixonBMB researcher Tracy Nixon and colleagues determined the first crystal structure of a bacterial enhancer binding protein (bEBP) bound by ATP.  bEBPs, which form a subset of the ubiquitous AAA+ ATPases, are activators that channel the energy of ATP binding and hydrolysis toward remodeling a protein factor called σ54.  This spatially altered protein is believed to separate the double stands of bacterial DNA to allow for the transcription of σ54-dependent genes by σ54’s associated RNA polymerase.  By comparing with structure of the same bEBP bound by ADP, large scale conformational changes pre- and post- ATP hydrolysis were observed involving the arginine finger of the bEBP.  This finding contributes toward a better understanding of how ATP driven molecular motors work in cellular processes. 

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Engagement of Arginine Finger to ATP Triggers Large Conformational Changes in NtrC1 AAA+ ATPase for Remodeling Bacterial RNA Polymerase
B. Chen, T.A. Sysoeva, S. Chowdhury, L. Guo, S De Carlo, J.A. Hanson, H. Yang, B. T. Nixon. Structure.  2010 Nov 18(11): 1420-1430.

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bEBP at Work

Courtesy of Nixon Lab

Movie Legend: This movie begins with an overlay of ATP-bound and ADP-bound structures of bEBP ribbon (top) or space filling (bottom) models. The overlay then fades with the stereo images oscillating between the ATP- and ADP- bound structures. Hydrolysis of ATP releases its binding to the bEBP arginine finger (green) and causes a rotation between bEBP's two rigid components (white and blue) plus a movement of the flexible upper loops (top red) bound to σ54. The upper loop movement triggers mechanical work on σ54 for spatial modification and subsequent release.

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