2hik
heterotrimeric PCNA sliding clamp
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OverviewOverview
DNA sliding clamps encircle DNA and provide binding sites for many DNA-processing enzymes. However, it is largely unknown how sliding clamps like proliferating cell nuclear antigen (PCNA) coordinate multistep DNA transactions. We have determined structures of Sulfolobus solfataricus DNA ligase and heterotrimeric PCNA separately by X-ray diffraction and in complex by small-angle X-ray scattering (SAXS). Three distinct PCNA subunits assemble into a protein ring resembling the homotrimeric PCNA of humans but with three unique protein-binding sites. In the absence of nicked DNA, the Sulfolobus solfataricus DNA ligase has an open, extended conformation. When complexed with heterotrimeric PCNA, the DNA ligase binds to the PCNA3 subunit and ligase retains an open, extended conformation. A closed, ring-shaped conformation of ligase catalyzes a DNA end-joining reaction that is strongly stimulated by PCNA. This open-to-closed switch in the conformation of DNA ligase is accommodated by a malleable interface with PCNA that serves as an efficient platform for DNA ligation.
About this StructureAbout this Structure
2HIK is a Protein complex structure of sequences from Sulfolobus solfataricus. Full crystallographic information is available from OCA.
ReferenceReference
A flexible interface between DNA ligase and PCNA supports conformational switching and efficient ligation of DNA., Pascal JM, Tsodikov OV, Hura GL, Song W, Cotner EA, Classen S, Tomkinson AE, Tainer JA, Ellenberger T, Mol Cell. 2006 Oct 20;24(2):279-91. PMID:17052461
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