FIGURE 4.

Substrate binding activity of Cas6 mutants. Uniformly ³²P-labeled CRISPR repeat RNA was incubated in the absence (−) or presence of increasing concentrations of wild-type or mutant Cas6 (1, 50, 200, and 500 nM). Formation of stable complexes was assessed by native gel mobility shift analysis. The positions of the free (RNA) and bound (RNP) substrate RNA are indicated.