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bioRxiv · 10.1101/2021.11.02.466367

CRISPR-Csx28 forms a Cas13b-activated membrane pore required for robust CRISPR-Cas adaptive immunity

VanderWal, A. R.·Park, J.-U.·Polevoda, B.·Kellogg, E. H.·O'Connell, M. R.
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Abstract

Type VI CRISPR-Cas systems use the RNA-guided RNase Cas13 to defend bacteria against viruses, and some of these systems encode putative membrane proteins that have unclear roles in Cas13-mediated defense. Here we show that Csx28, of Type VI-B2 systems, forms membrane pore structures to slow cellular metabolism upon viral infection, and this activity drastically increases anti-viral defense. High- resolution cryo-EM reveals that Csx28 exists unexpectedly as a detergent-encapsulated octameric pore, and we then show these Csx28 pores are membrane localized in vivo. Activation of Csx28 in vivo strictly requires sequence-specific recognition of viral mRNAs by Cas13b, and this activation results in Csx28-mediated membrane depolarization, slowed metabolism, and inhibition of sustained viral infection. Together, our work reveals an unprecedented mechanism by which Csx28 acts as a downstream, Cas13b-activated, effector protein that uses membrane perturbation as an anti-viral defense strategy.

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VanderWal, A. R., Park, J.-U., Polevoda, B., Kellogg, E. H., O'Connell, M. R.. 2021-11-02. CRISPR-Csx28 forms a Cas13b-activated membrane pore required for robust CRISPR-Cas adaptive immunity. https://doi.org/10.1101/2021.11.02.466367

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