Nucleotide-induced asymmetry within ATPase activator ring drives σ54–RNAP interaction and ATP hydrolysis
- 1Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA;
- 2BioCAT at Advanced Photon Source/Argonne National Laboratory, Illinois Institute of Technology, Argonne, Illinois 60439, USA
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↵3 These authors contributed equally to this work.
Abstract
It is largely unknown how the typical homomeric ring geometry of ATPases associated with various cellular activities enables them to perform mechanical work. Small-angle solution X-ray scattering, crystallography, and electron microscopy (EM) reconstructions revealed that partial ATP occupancy caused the heptameric closed ring of the bacterial enhancer-binding protein (bEBP) NtrC1 to rearrange into a hexameric split ring of striking asymmetry. The highly conserved and functionally crucial GAFTGA loops responsible for interacting with σ54–RNA polymerase formed a spiral staircase. We propose that splitting of the ensemble directs ATP hydrolysis within the oligomer, and the ring's asymmetry guides interaction between ATPase and the complex of σ54 and promoter DNA. Similarity between the structure of the transcriptional activator NtrC1 and those of distantly related helicases Rho and E1 reveals a general mechanism in homomeric ATPases whereby complex allostery within the ring geometry forms asymmetric functional states that allow these biological motors to exert directional forces on their target macromolecules.
Keywords
- AAA+ ATPase
- mechanochemical ATPases
- multimeric ATPases
- bacterial enhancer-binding protein (bEBP)
- σ54-dependent transcription
- σ54-dependent transcription activators
Footnotes
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↵6 Corresponding author
E-mail btn1{at}psu.edu
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Supplemental material is available for this article.
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Article is online at http://www.genesdev.org/cgi/doi/10.1101/gad.229385.113.
- Received August 25, 2013.
- Accepted October 16, 2013.
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