Determination of K
-values by fluorescence anisotropy measurements. 5 nM fluorescently labeled DNA/RNA primer/template substrate was titrated with PR-RT (closed circles) (A) or RNase H-(Q591-N751) (open circles) (B) as indicated. The fit of the curve to the data (equation 1) resulted in a KD-value of 9.1 nM (± 1.7) for the full length PFV PR-RT. The KD-value obtained for RNase H-(Q591-N751) is greater than 40 μM.