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Crystal Structure of Pseudomonas aeruginosa LigD polymerase domain with ATP and Manganese
Structural highlights
FunctionLIGD_PSEAE With Ku probably forms a non-homologous end joining (NHEJ) repair enzyme, which repairs dsDNA breaks (DSB) with reduced fidelity. Acts as a DNA ligase on singly nicked dsDNA, fills dsDNA gaps (3- or 4- nucleotide gaps, prefers a 5'-phosphate at the gap distal end, prefers dNTPs over rNTPs) (PubMed:20018881), has DNA-directed DNA polymerase activity (templated primer extension) and DNA-directed RNA polymerase activity (PubMed:15897197), adds 1 or 2 non-templated rNTP (or less well dNTP) to ssDNA or blunt-end dsDNA (primer extension). Has 3' resection activity, removing 3'-rNMPs from DNA using its 3'-ribonuclease and 3'-phosphatase activities sequentially. Resection requires a 2'-OH in the penultimate nucleoside position (i.e. a ribo- not deoxyribonucleoside) (PubMed:15897197), although the 3'-phosphatase activity does not, and its specific activity is 16-fold higher on a DNA substrate (PubMed:16046407). On appropriate substrates will extend a DNA primer to the end of the template strand and then incorporate a non-templated nucleotide.[1] [2] [3] The preference of the polymerase domain for rNTPs over dNTPs may be advantageous in quiescent cells where the dNTP pool may be limiting. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedDNA ligase D (LigD) is a large polyfunctional protein that participates in a recently discovered pathway of nonhomologous end-joining in bacteria. LigD consists of an ATP-dependent ligase domain fused to a polymerase domain (Pol) and a phosphoesterase module. The Pol activity is remarkable for its dependence on manganese, its ability to perform templated and nontemplated primer extension reactions, and its preference for adding ribonucleotides to blunt DNA ends. Here we report the 1.5-A crystal structure of the Pol domain of Pseudomonas LigD and its complexes with manganese and ATP/dATP substrates, which reveal a minimized polymerase with a two-metal mechanism and a fold similar to that of archaeal DNA primase. Mutational analysis highlights the functionally relevant atomic contacts in the active site. Although distinct nucleoside conformations and contacts for ATP versus dATP are observed in the cocrystals, the functional analysis suggests that the ATP-binding mode is the productive conformation for dNMP and rNMP incorporation. We find that a mutation of Mycobacterium LigD that uniquely ablates the polymerase activity results in increased fidelity of blunt-end double-strand break repair in vivo by virtue of eliminating nucleotide insertions at the recombination junctions. Thus, LigD Pol is a direct catalyst of mutagenic nonhomologous end-joining in vivo. Our studies underscore a previously uncharacterized role for the primase-like polymerase family in DNA repair. Atomic structure and nonhomologous end-joining function of the polymerase component of bacterial DNA ligase D.,Zhu H, Nandakumar J, Aniukwu J, Wang LK, Glickman MS, Lima CD, Shuman S Proc Natl Acad Sci U S A. 2006 Feb 7;103(6):1711-6. Epub 2006 Jan 30. PMID:16446439[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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