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. 2021 Feb 17;24(3):102201. doi: 10.1016/j.isci.2021.102201

Figure 1.

Figure 1

Structure of type IV-B CRISPR complex

See also Figures S1–S4 and Table S1.

(A) M. sp. JS623 plasmid-encoded CRISPR operons. Top: Type IV-B and I-E CRISPR loci present on pMCYCM02 megaplasmid. Bottom: Additional type IV-B locus encoded by pMCYCM03 megaplasmid. Genes predicted to encode RNP complex subunits are indicated with a gray rectangle.

(B) 3.9 Å-resolution cryo-EM reconstruction of type IV-B CRISPR complex. Cas7 subunits are colored blue and white, and five Cas11 subunits are colored as a yellow-orange-red gradient. Csf-bound RNA is green.

(C) Refined model for the Csf effector complex derived from the cryo-EM maps shown in (B).

(D) Schematic of Cas7-Cas11 interactions. Five Csf2-Cas11 interactions occur in this complex (labeled i – v).

(E) Positions of Cas11 contacts on Csf2 backbone, colored magenta as shown in panel D. Cas11 sits upon the Csf2-Csf2 interface.

(F) Cas11 binds at the interface with buried surface area of 505 Å2 (150 Å2 and 355 Å2 with Csf2.3 and Csf2.4, respectively). Cas11 is completely occluded from bound RNA. Csf2 subunits are intimately connected (1021 Å2) and make a network of contacts with bound RNA (∼1200 Å2 buried surface area per Csf2 subunit).