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Nat Struct Mol Biol. 2004 Jul;11(7):632-6. Epub 2004 Jun 20.

The clamp-loading complex for processive DNA replication.

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1
Department of Structural Biology, Biomolecular Engineering Research Institute, Suita, Osaka 565-0874, Japan.

Abstract

DNA polymerase requires two processing factors, sliding clamps and clamp loaders, to direct rapid and accurate duplication of genomic DNA. In eukaryotes, proliferating cell nuclear antigen (PCNA), the ring-shaped sliding clamp, encircles double-stranded DNA within its central hole and tethers the DNA polymerases onto DNA. Replication factor C (RFC) acts as the clamp loader, which correctly installs the sliding clamp onto DNA strands in an ATP-dependent manner. Here we report the three-dimensional structure of an archaeal clamp-loading complex (RFC-PCNA-DNA) determined by single-particle EM. The three-dimensional structure of the complex, reconstituted in vitro using a nonhydrolyzable ATP analog, reveals two components, a closed ring and a horseshoe-shaped element, which correspond to PCNA and RFC, respectively. The atomic structure of PCNA fits well into the closed ring, suggesting that this ternary complex represents a state just after the PCNA ring has closed to encircle the DNA duplex.

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PMID:
15208692
DOI:
10.1038/nsmb788
[Indexed for MEDLINE]
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