DNA polymerase beta: multiple conformational changes in the mechanism of catalysis

Conformational changes in the catalytic cycle of DNA polymerase beta were determined by stopped-flow fluorescence assay, utilizing a synthetic DNA primer/template with 2-aminopurine (2-AP) at the template position opposite the incoming dNTP. Two phases of fluorescence change were found in the stopped-flow fluorescence assay of the incorporation of the correct nucleotide dTTP. The rates of the two phases and their dependence on (dTTP) and (Mg2+) indicate that the fast conformational change is caused by the binding of MgdNTP and the slow conformational change is caused by the binding of the catalytic Mg2+ ion.