6MUU

Cryo-EM structure of Csm-crRNA binary complex in type III-A CRISPR-Cas system

Summary for 6MUU

• Entry DOI: 10.2210/pdb6muu/pdb
• Related: 6MUA 6MUR 6MUS 6MUT
• EMDB information: 9253 9254 9255 9256
• Descriptor: Uncharacterized protein Csm1, Uncharacterized protein Csm2, Uncharacterized protein Csm3, ... (7 entities in total)
• Functional Keywords: cryo-em structure, csm-crrna binary complex, type iii crispr-cas system, rna binding protein-rna complex, rna binding protein/rna
• Biological source: Thermococcus onnurineus; More
• Total number of polymer chains: 7
• Total formula weight: 267674.66

Authors

Jia, N.,Wang, C.,Eng, E.T.,Patel, D.J. (deposition date: 2018-10-23, release date: 2018-12-19, Last modification date: 2024-03-13)

Primary citation

Jia, N.,Mo, C.Y.,Wang, C.,Eng, E.T.,Marraffini, L.A.,Patel, D.J.
Type III-A CRISPR-Cas Csm Complexes: Assembly, Periodic RNA Cleavage, DNase Activity Regulation, and Autoimmunity.
Mol. Cell, 73:264-, 2019

PubMed Abstract: Type ΙΙΙ CRISPR-Cas systems provide robust immunity against foreign RNA and DNA by sequence-specific RNase and target RNA-activated sequence-nonspecific DNase and RNase activities. We report on cryo-EM structures of Thermococcus onnurineus Csm binary, Csm-target RNA and Csm-target RNA ternary complexes in the 3.1 Å range. The topological features of the crRNA 5'-repeat tag explains the 5'-ruler mechanism for defining target cleavage sites, with accessibility of positions -2 to -5 within the 5'-repeat serving as sensors for avoidance of autoimmunity. The Csm3 thumb elements introduce periodic kinks in the crRNA-target RNA duplex, facilitating cleavage of the target RNA with 6-nt periodicity. Key Glu residues within a Csm1 loop segment of Csm adopt a proposed autoinhibitory conformation suggestive of DNase activity regulation. These structural findings, complemented by mutational studies of key intermolecular contacts, provide insights into Csm complex assembly, mechanisms underlying RNA targeting and site-specific periodic cleavage, regulation of DNase cleavage activity, and autoimmunity suppression.

PubMed: 30503773
DOI: 10.1016/j.molcel.2018.11.007

Experimental method

ELECTRON MICROSCOPY (3 Å)