6S91

Cryo-EM structure of the Type III-B Cmr-beta bound to cognate target RNA and AMPPnP, state 2

Summary for 6S91

• Entry DOI: 10.2210/pdb6s91/pdb
• EMDB information: 10126
• Descriptor: CRISPR-associated protein, Cmr5 family, ZINC ION, PHOSPHOAMINOPHOSPHONIC ACID-ADENYLATE ESTER, ... (12 entities in total)
• Functional Keywords: crispr-cas, effector complex, nuclease, cyclic oligo-adenylate synthase, antiviral protein
• Biological source: Sulfolobus islandicus (strain REY15A); More
• Total number of polymer chains: 35
• Total formula weight: 895255.37

Authors

Sofos, N.,Montoya, G.,Stella, S. (deposition date: 2019-07-11, release date: 2020-07-08, Last modification date: 2020-09-16)

Primary citation

Sofos, N.,Feng, M.,Stella, S.,Pape, T.,Fuglsang, A.,Lin, J.,Huang, Q.,Li, Y.,She, Q.,Montoya, G.
Structures of the Cmr-beta Complex Reveal the Regulation of the Immunity Mechanism of Type III-B CRISPR-Cas.
Mol.Cell, 79:741-757.e7, 2020

PubMed Abstract: Cmr-β is a type III-B CRISPR-Cas complex that, upon target RNA recognition, unleashes a multifaceted immune response against invading genetic elements, including single-stranded DNA (ssDNA) cleavage, cyclic oligoadenylate synthesis, and also a unique UA-specific single-stranded RNA (ssRNA) hydrolysis by the Cmr2 subunit. Here, we present the structure-function relationship of Cmr-β, unveiling how binding of the target RNA regulates the Cmr2 activities. Cryoelectron microscopy (cryo-EM) analysis revealed the unique subunit architecture of Cmr-β and captured the complex in different conformational stages of the immune response, including the non-cognate and cognate target-RNA-bound complexes. The binding of the target RNA induces a conformational change of Cmr2, which together with the complementation between the 5' tag in the CRISPR RNAs (crRNA) and the 3' antitag of the target RNA activate different configurations in a unique loop of the Cmr3 subunit, which acts as an allosteric sensor signaling the self- versus non-self-recognition. These findings highlight the diverse defense strategies of type III complexes.

PubMed: 32730741
DOI: 10.1016/j.molcel.2020.07.008

Experimental method

ELECTRON MICROSCOPY (2.68 Å)