Cell, 9 February, 2023, DOI：https://doi.org/10.1016/j.cell.2023.01.026

Molecular basis of RADAR anti-phage supramolecular assemblies

Yina Gao, Xiu Luo, Peipei Li, Zhaolong Li, Feng Ye, Songqing Liu, Pu Gao

Abstract

Adenosine-to-inosine RNA editing has been proposed to be involved in a bacterial anti-phage defense system called RADAR. RADAR contains an adenosine triphosphatase (RdrA) and an adenosine deaminase (RdrB). Here, we report cryo-EM structures of RdrA, RdrB, and currently identified RdrA-RdrB complexes in the presence or absence of RNA and ATP. RdrB assembles into a dodecameric cage with catalytic pockets facing outward, while RdrA adopts both autoinhibited tetradecameric and activation-competent heptameric rings. Structural and functional data suggest a model in which RNA is loaded through the bottom section of the RdrA ring and translocated along its inner channel, a process likely coupled with ATP-binding status. Intriguingly, up to twelve RdrA rings can dock one RdrB cage with precise alignments between deaminase catalytic pockets and RNA-translocation channels, indicative of enzymatic coupling of RNA translocation and deamination. Our data uncover an interesting mechanism of enzymatic coupling and anti-phage defense through supramolecular assemblies.

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