Fig. 4: Conformational changes of I-D Cascade and PRD locking upon PAM recognition.
From: Structural rearrangements allow nucleic acid discrimination by type I-D Cascade
a Domain organization of Cas10d. Cas10d has a Cas3″ nuclease domain at the N-terminus (Cas3″, purple-maroon), a small subunit (Cas11) domain embedded within the C-terminus (Cas11, pink), and a PAM recognition domain (PRD, dark purple). b Structure of Cas10d. Domains are colored as in a. c Structure of type I-D complex bound to target ssRNA. There is no discernable density for the PRD (PRD-inactive). d Vector shift between conformations with and without PAM-recognition. Upon PAM recognition, the Cas11d and Cas10d subunits appear to shift downward ~5 Å. e Structure of type I-D complex upon PAM-dependent dsDNA target binding shows the PRD becomes ordered (PRD engaged). f Top-down view of PRD disengaged conformation. Without PAM recognition, the PRD density disappears at a higher threshold and the NTS is not present. g Top–down view of PRD engaged conformation. PRD density is visible and NTS density becomes disordered after the PAM. Subunits are colored as in Fig. 1 with Cas10d colored by domain.
