8Q41

Crystal structure of Can2 (E341A) bound to cA4 and TTTAAA ssDNA

Summary for 8Q41

• Entry DOI: 10.2210/pdb8q41/pdb
• Related PRD ID: PRD_002431
• Descriptor: DUF1887 family protein, DNA (5'-D(*TP*TP*AP*AP*A)-3'), Cyclic tetraadenosine monophosphate (cA4), ... (5 entities in total)
• Functional Keywords: can2, cyclic oligoadenylates, ca4, carf, crispr ancillary nuclease, protein-dna complex, dna binding protein
• Biological source: Thermoanaerobacter brockii subsp. finnii Ako-1; More
• Total number of polymer chains: 5
• Total formula weight: 107736.04

Authors

Jungfer, K.,Sigg, A.,Jinek, M. (deposition date: 2023-08-04, release date: 2023-11-22, Last modification date: 2024-01-24)

Primary citation

Jungfer, K.,Sigg, A.,Jinek, M.
Substrate selectivity and catalytic activation of the type III CRISPR ancillary nuclease Can2.
Nucleic Acids Res., 52:462-473, 2024

PubMed Abstract: Type III CRISPR-Cas systems provide adaptive immunity against foreign mobile genetic elements through RNA-guided interference. Sequence-specific recognition of RNA targets by the type III effector complex triggers the generation of cyclic oligoadenylate (cOA) second messengers that activate ancillary effector proteins, thus reinforcing the host immune response. The ancillary nuclease Can2 is activated by cyclic tetra-AMP (cA4); however, the mechanisms underlying cA4-mediated activation and substrate selectivity remain elusive. Here we report crystal structures of Thermoanaerobacter brockii Can2 (TbrCan2) in substrate- and product-bound complexes. We show that TbrCan2 is a single strand-selective DNase and RNase that binds substrates via a conserved SxTTS active site motif, and reveal molecular interactions underpinning its sequence preference for CA dinucleotides. Furthermore, we identify a molecular interaction relay linking the cA4 binding site and the nuclease catalytic site to enable divalent metal cation coordination and catalytic activation. These findings provide key insights into the molecular mechanisms of Can2 nucleases in type III CRISPR-Cas immunity and may guide their technological development for nucleic acid detection applications.

PubMed: 38033326
DOI: 10.1093/nar/gkad1102

Experimental method

X-RAY DIFFRACTION (2.38 Å)