Solution structure of a viral DNA repair polymerase

DNA polymerase X (Pol X) from the African swine fever virus (ASFV) specific ally binds intermediates in the single-nucleotide base-excision repair proc ess, an activity indicative of repair function. In addition, Pol X catalyze s DNA polymerization with low nucleotide-insertion fidelity. The structural mechanisms by which DNA polymerases confer high or low fidelity in DNA pol ymerization remain to be elucidated. The three-dimensional structure of Pol X has been determined. Unlike other DNA polymerases, Pol X is formed from only a palm and a C-terminal subdomain. Pol X has a novel palm subdomain fo ld, containing a positively charged helix at the DNA binding surface. Purin e deoxynucleoside triphosphate (dNTP) substrates bind between the palm and C-terminal subdomain, at a dNTP-binding helix, and induce a unique conforma tion in Pol X. The purine dNTP-bound conformation and high binding affinity for dGTP-Mg2+ of Pol X may contribute to its low fidelity.