title: Open clamp structure in the clamp-loading complex visualized by electron microscopic image analysis.
abstract: Ring-shaped sliding clamps and clamp loader ATPases are essential factors for rapid and accurate DNA replication. The clamp ring is opened and resealed at the primer-template junctions by the ATP-fueled clamp loader function. The processivity of the DNA polymerase is conferred by its attachment to the clamp loaded onto the DNA. In eukarya and archaea, the replication factor C (RFC) and the proliferating cell nuclear antigen (PCNA) play crucial roles as the clamp loader and the clamp, respectively. Here, we report the electron microscopic structure of an archaeal RFC-PCNA-DNA complex at 12-A resolution. This complex exhibits excellent fitting of each atomic structure of RFC, PCNA, and the primed DNA. The PCNA ring retains an open conformation by extensive interactions with RFC, with a distorted spring washer-like conformation. The complex appears to represent the intermediate, where the PCNA ring is kept open before ATP hydrolysis by RFC.
authors.affiliation: Department of Structural Biology, Biomolecular Engineering Research Institute, 6-2-3 Furuedai, Suita, Osaka 565-0874, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Miyata
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Takuji
authors.initials: T
authors.lastname: Oyama
authors.forename: Kouta
authors.initials: K
authors.lastname: Mayanagi
authors.forename: Yoshizumi
authors.initials: Y
authors.lastname: Ishino
authors.forename: Kosuke
authors.initials: K
authors.lastname: Morikawa
mesh_terms: D004261:DNA Replication; D019641:DNA, Archaeal / Q000737:chemistry / Q000648:ultrastructure*; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000648:ultrastructure*; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D018809:Proliferating Cell Nuclear Antigen / Q000737:chemistry / Q000648:ultrastructure*; D011487:Protein Conformation; D020027:Pyrococcus furiosus / Q000235:genetics* / Q000378:metabolism
chemical_list: D019641:DNA, Archaeal; D018809:Proliferating Cell Nuclear Antigen; C072146:Pfu DNA polymerase; D004259:DNA-Directed DNA Polymerase