Fig. 3
From: Target preference of Type III-A CRISPR-Cas complexes at the transcription bubble
Cryo-EM structures of target RNA-bound TthCsm and modeling of the TthCsm-TEC complex. a Cryo-EM structure and model of target RNA-bound TthCsm. TthCsm subunits, crRNA, and target RNA are labeled in the different views. Each view is rotated by 90˚, as indicated by arrows. b Detailed view of the discontinuous crRNA and target RNA hybrid, showing the base pairs fit into the EM density of the RNA hybrid. A loop in each Csm3 subunit inserts after every 5-nt segment and flips out the 6th base. The EM density of the crRNA:target RNA hybrid and the modeled crRNA strand are colored dark blue, and the modeled target RNA strand is colored red-orange. The EM density and model corresponding to the third Csm3 subunit (Csm3.3) is colored light blue. c Models of RNA-bound TthCsm and the TEC complex fit into the negative stain EM map. The HD domain of Cas10/Csm1 is colored pink, the nontemplate strand (NTS) and template strand (TS) are colored red, the RNA transcript is colored orange, and the crRNA is colored dark blue. A dotted orange line is used to represent the segment of RNA between the RNA exit channel and the TthCsm bound target sequence. TthCsm is colored gray and the protein subunits of the RNAP are colored light blue. The orientation of the RNAP was determined using the features of the EM density map (3D model 8 in Fig. 2)
