Summary information and primary citation
- PDB-id
- 7ygl; DSSR-derived features in text and JSON formats
- Class
- hydrolase
- Method
- X-ray (2.5 Å)
- Summary
- Crystal structure of the ring nuclease sso2081 from saccharolobus solfataricus in complex with a4>p cleavage intermediate
- Reference
- Du L, Zhang D, Luo Z, Lin Z (2023): "Molecular basis of stepwise cyclic tetra-adenylate cleavage by the type III CRISPR ring nuclease Crn1/Sso2081." Nucleic Acids Res., 51, 2485-2495. doi: 10.1093/nar/gkad101.
- Abstract
- The cyclic oligoadenylates (cOAs) act as second messengers of the type III CRISPR immunity system through activating the auxiliary nucleases for indiscriminate RNA degradation. The cOA-degrading nucleases (ring nucleases) provide an 'off-switch' regulation of the signaling, thereby preventing cell dormancy or cell death. Here, we describe the crystal structures of the founding member of CRISPR-associated ring nuclease 1 (Crn1) Sso2081 from Saccharolobus solfataricus, alone, bound to phosphate ions or cA4 in both pre-cleavage and cleavage intermediate states. These structures together with biochemical characterizations establish the molecular basis of cA4 recognition and catalysis by Sso2081. The conformational changes in the C-terminal helical insert upon the binding of phosphate ions or cA4 reveal a gate-locking mechanism for ligand binding. The critical residues and motifs identified in this study provide a new insight to distinguish between cOA-degrading and -nondegrading CARF domain-containing proteins.