Fig. 4: Binding of invasive non-self RNA target induces large conformational changes of gRAMP^crRNA -TPR-CHAT complex.

a Schematic drawing for the sequences of crRNA and non-self RNA target. Segments that can be traced are in color, while disordered segments are in gray. Schematic (b) and ribbon (c) representations of cryo-EM structure of gRAMP^crRNA-TPR-CHAT complex bound to non-self RNA target. TPR-CHAT protein is shown in a surface view. The expanded view shows the detailed interactions between 3′- flanking sequence and protein residues in gRAMP and TPR-CHAT. d Structural comparison between gRAMP^crRNA-TPR-CHAT complex before and after binding to non-self RNA target. Vector length correlates with the domain movement scale. e Detailed conformational changes induced by non-self target RNA binding. The gRAMP^crRNA-TPR-CHAT complex is shown in gray, and gRAMP^crRNA-TPR-CHAT-target RNA^non-self complex is shown in color. The blue arrow indicates the movement scale of the secondary structures in the CHAT protease catalytic pocket. Structures of CHAT protease domain in gRAMP^crRNA -TPR-CHAT before (g) and after (f) non-self RNA target binding. The CHAT domain is shown in a surface view. The red surface indicates the position of catalytic residues H585 and C627. h Structural comparison of the catalytic pockets among gRAMP^crRNA-TPR-CHAT (in gray), gRAMP^crRNA-TPR-CHAT-target RNA^non-self (in marine), and the active separase protease domain from the thermophilic fungus Chaetomium thermophilum (in violet, PDB 5FC3).