Figure 1.

Type I-D arrangement of the adaptation module and the CRISPR array. Downstream of cas2 is the 212 bp leader sequence. Conserved regions obtained from MAFFT alignments of 25 leaders reveal conserved motifs predominantly at the repeat distal end with increasing sequence variability at the repeat proximal end. Sequence conservation is summarized in Weblogo3 depictions (Crooks et al., 2004). Leader truncations from the repeat-distal end for experimental investigation of conserved motifs are indicated with red dashed lines.