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bioRxiv · 10.1101/2022.06.16.496122

Sequence-independent substrate selection by the eukaryotic wobble base deaminase ADAT2/3 involves multiple protein domains and distortion of the tRNA anticodon loop

Dolce, L. G.·Zimmer, A. A.·Tengo, L.·Weis, F.·Rubio, M. A. T.·Alfonzo, J. D.·Kowalinski, E.
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Abstract

The essential deamination of adenosine A34 to inosine at the wobble base is the individual tRNA modification with the greatest effects on mRNA decoding, empowering a single tRNA to translate three different codons. To date, many aspects of how eukaryotic deaminases specifically select their multiple substrates remain unclear. Here, using cryo-EM, we present the first structure of a eukaryotic ADAT2/3 deaminase bound to a full-length tRNA, revealing that the enzyme distorts the anticodon loop, but in contrast to the bacterial enzymes, selects its substrate via sequence-independent contacts of eukaryote-acquired flexible or intrinsically unfolded motifs distal from the conserved catalytic core. A novel gating mechanism for substrate entry to the active site is identified. Our multi-step tRNA recognition model yields insights into how RNA editing by A34 deamination evolved, shaped the genetic code, and directly impacts the eukaryotic proteome.

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Dolce, L. G., Zimmer, A. A., Tengo, L., Weis, F., Rubio, M. A. T., Alfonzo, J. D., Kowalinski, E.. 2022-06-16. Sequence-independent substrate selection by the eukaryotic wobble base deaminase ADAT2/3 involves multiple protein domains and distortion of the tRNA anticodon loop. https://doi.org/10.1101/2022.06.16.496122

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