Conformational distortion of sugar moieties in the RecA-bound DNA structure determined by a simulated annealing method.

We recently reported an NMR study indicating that the DNA structure bound to RecA protein contains a novel deoxyribose-base stacking interaction. Although the final structure calculated by the simulated annealing was well defined, the type of sugar puckers was neither pure C2'-endo nor C3'-endo, but something in between. This implies that the sugar moieties in the RecA-bound state actually take an intermediate puckering, but we can not exclude the possibility that RecA-bound DNA takes multiple conformations between the S-type and N-type of sugar puckers. In either case, the DNA structure within RecA filaments shows a unique property that is distinct from canonical DNA structures.