Download MendeleyStructures of the Cmr-beta Complex Reveal the Regulation of the Immunity Mechanism of Type III-B CRISPR-Cas.
Sofos, N., Feng, M., Stella, S., Pape, T., Fuglsang, A., Lin, J., Huang, Q., Li, Y., She, Q., Montoya, G.(2020) Mol Cell 79: 741-757.e7
- PubMed: 32730741
- DOI: https://doi.org/10.1016/j.molcel.2020.07.008
- Primary Citation of Related Structures:
6S6B, 6S8B, 6S8E, 6S91, 6SH8, 6SHB, 6SIC - 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.
Organizational Affiliation:
Structural Molecular Biology Group, Novo Nordisk Foundation Centre for Protein Research, Faculty of Health and Medical Sciences, University of Copenhagen, Blegdamsvej 3-B, 2200 Copenhagen, Denmark.
