Dependence of KSHV Pr (WT) specific activity on the relative concentration of KSHV Pr S114A. Experimental concentrations of KSHV Pr are 2 (open diamonds) and 0.5 (filled circles) μM. Theoretical curves for the relative specific activities are shown at KSHV Pr concentrations of 2 (thin lines) and 0.5 (thick lines) μM. If the heterodimer of KSHV Pr and KSHV Pr S114A is active (dashed lines) or inactive (solid lines), the specific activity is expected to increase or decrease, respectively. The experimental data are in agreement with the heterodimer being active. Note that specific activity at 5.5 μM, which is the highest concentration of KSHV Pr S114A in this experiment, was not detectable, verifying that KSHV Pr S114A does not display any activity at these concentrations.