FIGURE 2.

Activity on AP sites within 3′ overhangs. A, representative denaturing PAGE analysis of reactions incubated for 15 min at 37 ºC with 5 nm Ku (Ku) and 1 nm substrates 1–4 (reaction with 5′ overhang substrate 1 shown for comparative purposes), with substrate end structure varied as described in the graphics shown in panel B. OH, control reactions with substrates (Sub.) cleaved by alkali. Alkali cleavage generates a product (P) with a 3′-PO₄ terminus with faster mobility than the 3′α,β-unsaturated aldehyde terminus generated by Ku. B, velocities for substrates 2, 3, and 4 were determined from the slope of reaction progression as measured after 15, 30, and 60 min. Velocity averages and standard deviations (error bars) are from the results of three independent experiments. Substrate 2 velocity was undetectable (UD). 5P, 5′-phosphate.