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bioRxiv · 10.1101/2022.08.22.504715

Structural and functional insights into the type III-E CRISPR-Cas immunity

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.
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Abstract

The type III-E CRISPR-Cas system comprises a Cas effector (gRAMP), a TPR-CHAT and several ancillary proteins. However, both the structural features of gRAMP and the immunity mechanism remain unknown for this system. Here, we report a series of structures of gRAMP-crRNA, either its alone or in complex with target RNA or TPR-CHAT (called Craspase), and Craspase complexed with cognate (CTR) or non-cognate target RNA (NTR). Importantly, the 3 anti-tag region of NTR and CTR bind at two distinct channels in the 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 CRISPR-Cas system.

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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.. 2022-08-22. Structural and functional insights into the type III-E CRISPR-Cas immunity. https://doi.org/10.1101/2022.08.22.504715

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