Figure 5.

Function of aromatic residues flanking K31. A and B. Representative reactions performed with 5 nM WT human Ku heterodimers or Ku heterodimers with Ku70 K160A, Ku70 K160A and Y30A, or Ku70 K160A, Y30A and Y32A substitutions. A. Reactions used the standard AP substrate and were incubated for 15 min. B. Reactions used a variant substrate with an AP site located an additional nucleotide further from the 5′ terminus, relative to the substrate used in panel A (see cartoon), and were incubated for 30 min. C. Average velocities and standard deviations were determined from three independent experiments, and expressed relative to the average velocity observed with a Ku heterodimer containing Ku70 with the K160A substitution.