Fig. 2: Structures of Cognate target RNA (CTR)-bound LlCsm complex.

Numbers in white indicate names of the subunit where N or N.m represent CsmN (or the mth CsmN). Key secondary elements are labeled. The crRNA and CTR are colored black and red, respectively. a Schematic representation, electron potential density, and cartoon representation of CTR-43 with stoichiometry 1₁2₃3₄4₁5₁crRNA₁Target₁. Italicized numbers in black indicate the buried solvent-accessible surface of the corresponding subunits in Ų. The relative positions of crRNA 5′-tag and the CTR 3′-PFS are highlighted. The boxed image at the top displays three α-helices of LLCsm1: α12, α17, and α21 that orient the positively charged N-terminus towards the 3′-PFS of CTR, thus forming a favorable protein-RNA interaction. The boxed image towards the bottom displays the Csm3-Csm4 pocket where the 5′-tag of crRNA traverses. b Schematic representation and overall structure of CTR-32 with stoichiometry 1₁2₂3₃4₁5₁R₁T₁. The crRNA and CTR are colored black and red, respectively. The relative positions of crRNA 5′-tag and the CTR 3′-PFS are highlighted. c Ribbon representation of CTR-43 (gray) and CTR-32 (colored) with their Csm3 subunits superimposed highlighting structural differences in other subunits.