FIGURE 3.

Cleavage activity of Cas6 mutants. (A) Uniformly ³²P-labeled CRISPR repeat RNA was incubated in the absence (−) or presence of increasing concentrations of wild-type or mutant Cas6 (10, 50, and 500 nM) followed by separation on a 15% denaturing (7 M urea) polyacrylamide gel. The 5′ and 3′ cleavage products are indicated to the right. (B) Purified wild-type (wt) and mutant Cas6 proteins were analyzed by SDS-PAGE and Coomassie blue staining. Molecular weight markers are indicated in kilodaltons.