Download MendeleyThe E. coli clamp loader can actively pry open the beta-sliding clamp
Paschall, C.O., Thompson, J.A., Marzahn, M.R., Chiraniya, A., Hayner, J.N., O'Donnell, M., Robbins, A.H., McKenna, R., Bloom, L.B.(2011) J Biol Chem 286: 42704-42714
- PubMed: 21971175
- DOI: https://doi.org/10.1074/jbc.M111.268169
- Primary Citation of Related Structures:
3PWE - PubMed Abstract:
Clamp loaders load ring-shaped sliding clamps onto DNA. Once loaded onto DNA, sliding clamps bind to DNA polymerases to increase the processivity of DNA synthesis. To load clamps onto DNA, an open clamp loader-clamp complex must form. An unresolved question is whether clamp loaders capture clamps that have transiently opened or whether clamp loaders bind closed clamps and actively open clamps. A simple fluorescence-based clamp opening assay was developed to address this question and to determine how ATP binding contributes to clamp opening. A direct comparison of real time binding and opening reactions revealed that the Escherichia coli γ complex binds β first and then opens the clamp. Mutation of conserved "arginine fingers" in the γ complex that interact with bound ATP decreased clamp opening activity showing that arginine fingers make an important contribution to the ATP-induced conformational changes that allow the clamp loader to pry open the clamp.
Organizational Affiliation:
Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, Florida 32610-0245.
