FIG. 3.

Mobility shift of core-type DNA by mutant C65-Ints. COC" (36 bp) and C" (21 bp plus 3-base hairpin) fragments (0.01 μM) were incubated with different concentrations of C65-Int R212Q (Q) and Y342F (F) mutants. Titrations on COC" DNA were in the absence (A) and in the presence (B) of equimolar non-att DNA (276 bp), which functions as a nonspecific (non-spec.) binding competitor. Another recombination-deficient mutant, C65-K235A, is competent for DNA binding and is included for comparison (B, lanes 3 and 4). It displays 68% specific binding at concentrations that saturate non-att DNA. (C) Full-length Int mutants R212Q (IntQ) and Y342F (IntF) retard a half-att site (half-core C") more than their respective C65-Ints (C65Q and C65F).