The Bacterial DnaC Helicase Loader Is a DnaB Ring Breaker
| Autor: | Iris V. Hood, Ernesto Arias-Palomo, Valerie L. O’Shea, James M. Berger |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
DNA Replication
Models Molecular Article General Biochemistry Genetics and Molecular Biology Geobacillus stearothermophilus 03 medical and health sciences chemistry.chemical_compound Scattering Small Angle Escherichia coli dnaB helicase Polymerase 030304 developmental biology Genetics 0303 health sciences biology Biochemistry Genetics and Molecular Biology(all) Escherichia coli Proteins 030302 biochemistry & molecular biology DNA replication Helicase RNA Helicase A Protein Structure Tertiary Microscopy Electron Dodecameric protein chemistry biology.protein Biophysics bacteria DnaB Helicases dnaC DNA |
| Zdroj: | Cell. 153:438-448 |
| ISSN: | 0092-8674 |
| Popis: | Dedicated AAA+ ATPases help deposit hexameric ring-shaped helicases onto DNA to promote replication in cellular organisms. To understand how loading occurs, we used negative-stain electron microscopy and small-angle X-ray scattering to determine the ATP-bound structure of the intact E. coli DnaB•DnaC helicase/loader complex. The 480 kDa dodecamer forms a three-tiered assembly, in which DnaC adopts a spiral configuration that remodels N-terminal scaffolding and C-terminal motor regions of DnaB to produce a clear break in the helicase ring. Surprisingly, DnaC’s AAA+ fold is dispensable for ring remodeling, as the isolated helicase-binding domain of DnaC can both load DnaB onto DNA and increase the efficiency by which the helicase acts on substrates in vitro. Our data demonstrate that DnaC opens DnaB by a mechanism akin to that of polymerase clamp loaders, and indicate that bacterial replicative helicases, like their eukaryotic counterparts, possess auto-regulatory elements that influence how the hexameric motor domains are loaded onto and unwind DNA. |
| Databáze: | OpenAIRE |
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