Figure 4.

The activity of gp74 in the presence of Ni²⁺, but not Zn²⁺, is mediated by pH. Agarose gel (1%) electrophoresis analysis of lambda phage DNA digestion by gp74 in the presence of (A) Ni²⁺ ions or (B) Zn²⁺ ions. At pH 5, reactions contained 25 μg/mL of λ DNA, 48 μg/mL of gp74, and 0.5 mM of either Ni²⁺ or Zn²⁺ ions. At pH 6–8, reactions contained 50 μg/mL of lambda phage DNA, 48 μg/mL of gp74, and 0.5 mM of either Ni²⁺ or Zn²⁺ ions.