Calcium is a cofactor of polymerization but inhibits pyrophosphorolysis by the Sulfolobus solfataricus DNA polymerase Dpo4.

Irimia A, Zang H, Loukachevitch LV, Eoff RL, Guengerich FP, Egli M
Biochemistry. 2006 45 (19): 5949-56

PMID: 16681366 · DOI:10.1021/bi052511+

Y-Family DNA polymerase IV (Dpo4) from Sulfolobus solfataricus serves as a model system for eukaryotic translesion polymerases, and three-dimensional structures of its complexes with native and adducted DNA have been analyzed in considerable detail. Dpo4 lacks a proofreading exonuclease activity common in replicative polymerases but uses pyrophosphorolysis to reduce the likelihood of incorporation of an incorrect base. Mg(2+) is a cofactor for both the polymerase and pyrophosphorolysis activities. Despite the fact that all crystal structures of Dpo4 have been obtained in the presence of Ca(2+), the consequences of replacing Mg(2+) with Ca(2+) for Dpo4 activity have not been investigated to date. We show here that Ca(2+) (but not Ba(2+), Co(2+), Cu(2+), Ni(2+), or Zn(2+)) is a cofactor for Dpo4-catalyzed polymerization with both native and 8-oxoG-containing DNA templates. Both dNTP and ddNTP are substrates of the polymerase in the presence of either Mg(2+) or Ca(2+). Conversely, no pyrophosphorolysis occurs in the presence of Ca(2+), although the positions of the two catalytic metal ions at the active site appear to be very similar in mixed Mg(2+)/Ca(2+)- and Ca(2+)-form Dpo4 crystals.

MeSH Terms (9)

Base Sequence Biopolymers Calcium Cations, Divalent Diphosphates DNA-Directed DNA Polymerase DNA Primers Models, Molecular Sulfolobus solfataricus

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