Fig. 1.

The composition of the Cascade complex. (A) Schematic diagram of the CRISPR/cas gene cluster of E. coli K12 W3110. Repeats and spacers are indicated by diamonds and rectangles, respectively. A palindrome in the repeat is marked by convergently pointing arrows. Protein family nomenclature is as described in (11, 12). (B) Coomassie blue—stained SDS-polyacrylamide gel of the affinity purified protein complex using either the N-terminal StrepII-tag (S) or C-terminal His-tag (H) of each of the subunits CasB, CasC, CasD, or CasE as bait. Asterisks indicate the 5.5 kD larger double-tagged subunits. Marker sizes in kilodaltons on the left; location of untagged subunits on the right.