FIG. 3.

ICP8 increases the processivity of UL12 on dsDNA. The nuclease assay was performed by first preincubating all reactants in the absence of Mg²⁺ for 2 min at 37°C, to allow for binding of the enzymes to the substrate DNA. The assay was initiated with the addition of MgCl₂ to 1 mM. At 2 min (marked with arrow), 2 μl of 44 mg/ml heparin (4 mg/ml final) or water (controls) was added. Closed squares, UL12 + ICP8, no heparin; open squares, UL12 + ICP8 + heparin; closed circles, UL12 no heparin; open circles, UL12 + heparin. Protein concentrations were the same as in Fig. 1.