Journal
GENES & DEVELOPMENT
Volume 27, Issue 22, Pages 2500-2511Publisher
COLD SPRING HARBOR LAB PRESS, PUBLICATIONS DEPT
DOI: 10.1101/gad.229385.113
Keywords
AAA(+) ATPase; mechanochemical ATPases; multimeric ATPases; bacterial enhancer-binding protein (bEBP); sigma 54-dependent transcription; sigma 54-dependent transcription activators
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Funding
- U.S. Department of Energy, Basic Energy Sciences, Office of Science [W-31-109-ENG-38,, DE-AC02-05CH11231, DEAC02-98CH10886]
- National Institutes of Health [RR-08630]
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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 sigma 54-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 sigma 54 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.
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