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Publication Abstract from PubMed

In the type III-E CRISPR-Cas system, a Cas effector (gRAMP) is associated with a TPR-CHAT to form Craspase (CRISPR-guided caspase). However, both the structural features of gRAMP and the immunity mechanism remain unknown for this system. Here, we report structures of gRAMP-crRNA and gRAMP:cRNA:target RNA as well as structures of Craspase and Craspase complexed with cognate target RNA (CTR) or non-cognate target RNA (NTR). Importantly, the 3' anti-tag region of NTR and CTR binds at two distinct channels in Craspase, and CTR with a non-complementary 3' anti-tag induces a marked conformational change of the TPR-CHAT, which allosterically activates its protease activity to cleave an ancillary protein Csx30. This cleavage then triggers an abortive infection as the antiviral strategy of the type III-E system. Together, our study provides crucial insights into both the catalytic mechanism of the gRAMP and the immunity mechanism of the type III-E system.

Target RNA activates the protease activity of Craspase to confer antiviral defense.,Liu X, Zhang L, Wang H, Xiu Y, Huang L, Gao Z, Li N, Li F, Xiong W, Gao T, Zhang Y, Yang M, Feng Y Mol Cell. 2022 Dec 1;82(23):4503-4518.e8. doi: 10.1016/j.molcel.2022.10.007. Epub , 2022 Oct 27. PMID:36306795^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.