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. Author manuscript; available in PMC: 2016 Dec 2.
Published in final edited form as: Nature. 2016 Feb 10;530(7591):499–503. doi: 10.1038/nature16995

Figure 2. PAM recognition by Cse1 subunit of Cascade.

Figure 2

a, b, Detailed views featuring PAM recognition by the glutamine-wedge (and its involvement in target DNA strand displacement), glycine-loop, and lysine-finger of Cse1. The 2FO-FC electron density map is displayed at 1.5 σ. c, Summarization of the five interference PAMs in E. coli Type I-E CRISPR system, with the observed Cascade contacts marked. d, Top-down views of PAM recognition at each base-pair. Left: stringent recognition of PAM-1. Middle: shape complementarity to PAM-2. Right: Electrostatic contacts to PAM-3 and -4. e, Mutagenesis assayed by Cascade-binding (EMSA) and f, Cas3-mediated DNA cleavage to evaluate the observed PAM contacts.