Characterization of an African swine fever virus 20-kDa DNA polymerase involved in DNA repair.


African swine fever virus (ASFV) encodes a novel DNA polymerase, constituted of only 174 amino acids, belonging to the polymerase (pol) X family of DNA polymerases. Biochemical analyses of the purified enzyme indicate that ASFV pol X is a monomeric DNA-directed DNA polymerase, highly distributive, lacking a proofreading 3'-5'-exonuclease, and with a poor discrimination against dideoxynucleotides. A multiple alignment of family X DNA polymerases, together with the extrapolation to the crystal structure of mammalian DNA polymerase beta (pol beta), showed the conservation in ASFV pol X of the most critical residues involved in DNA binding, nucleotide binding, and catalysis of the polymerization reaction. Therefore, the 20-kDa ASFV pol X most likely represents the minimal functional version of an evolutionarily conserved pol beta-type DNA polymerase core, constituted by only the "palm" and "thumb" subdomains. It is worth noting that such an "unfingered" DNA polymerase is able to handle templated DNA polymerization with a considerable high fidelity at the base discrimination level. Base excision repair is considered to be a cellular defense mechanism repairing modified bases in DNA. Interestingly, the fact that ASFV pol X is able to conduct filling of a single nucleotide gap points to a putative role in base excision repair during the ASFV life cycle.



Historical Protein Properties (MW, pI, ...), Exonuclease Activity, Source / Purification, Structure and Structure/Function, Nucleotide Incorporation


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Polymerase Reference Property Result Context
ASFV pol X Oliveros M1997 Molecular Weight 2E+04 Dalton
ASFV pol X Oliveros M1997 Polymerase Catalytic Residue Amino Acids Asp49,Asp51,Asp100
ASFV pol X Oliveros M1997 3-5' Exonuclease (proofreading) No
ASFV pol X Oliveros M1997 Cloned or native Cloned in E. coli
ASFV pol X Oliveros M1997 Tagged No
ASFV pol X Oliveros M1997 Full length or truncated Full length
ASFV pol X Oliveros M1997 Gap Filling Yes

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