Evan A Schwartz, Jack P K Bravo, Mohd Ahsan, Luis A Macias, Caitlyn L McCafferty, Tyler L Dangerfield, Jada N Walker, Jennifer S Brodbelt, Giulia Palermo, Peter C Fineran, Robert D Fagerlund, David W Taylor
CRISPR-Cas are adaptive immune systems in bacteria and archaea that utilize CRISPR RNA-guided surveillance complexes to target complementary RNA or DNA for destruction1-5 . Target RNA cleavage at regular intervals is characteristic of type III effector complexes6-8 . Here, we determine the structures of the Synechocystis type III-Dv complex, an apparent evolutionary intermediate from multi-protein to single-protein type III effectors9,10 , in pre- and post-cleavage states. The structures show how multi-subunit fusion proteins in the effector are tethered together in an unusual arrangement to assemble into an active and programmable RNA endonuclease and how the effector utilizes a distinct mechanism for target RNA seeding from other type III effectors...
April 18, 2024: Nature Communications