Fig. 4.

Type 2 (relaxed-specificity) mutants recognize single-base variants of χ. Yield of variant χ-containing ssDNA produced by a mutant enzyme is plotted versus position of the canonical χ sequence. Canonical recognition is the left-most bar; solid, crosshatched, or white bars denote substitution of adenine, thymine, or cytosine at that position, respectively (Table S1). Final yields (± SD) from at least two independent experiments are plotted. There is only one χ sequence in the proper orientation, and because RecBCD can enter from either DNA end, the efficiency of χ recognition is at least twofold higher.