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bioRxiv · 10.1101/2021.04.20.440599

Structures of a deAMPylation complex rationalise the switch between antagonistic catalytic activities of FICD

Perera, L. A.·Preissler, S.·Zaccai, N. R.·Prevost, S.·Devos, J. M.·Haertlein, M.·Ron, D.
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Abstract

The endoplasmic reticulum (ER) Hsp70 chaperone BiP is regulated by AMPylation, a reversible inactivating post-translational modification. Both BiP AMPylation and deAMPylation are catalysed by a single ER-localised enzyme, FICD. Here we present long-sought crystallographic and solution structures of a deAMPylation Michaelis complex formed between mammalian AMPylated BiP and FICD. The latter, via its tetratricopeptide repeat domain, binds a surface that is specific to ATP-state Hsp70 chaperones, explaining the exquisite selectivity of FICD for BiPs ATP-bound conformation both when AMPylating and deAMPylating Thr518. The eukaryotic deAMPylation mechanism thus revealed, rationalises the role of the conserved Fic domain Glu234 as a gatekeeper residue that both inhibits AMPylation and facilitates hydrolytic deAMPylation catalysed by dimeric FICD. These findings point to a monomerisation-induced increase in Glu234 flexibility as the basis of an oligomeric state-dependent switch between FICDs antagonistic activities, despite a similar mode of engagement of its two substrates -- unmodified and AMPylated BiP.

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Perera, L. A., Preissler, S., Zaccai, N. R., Prevost, S., Devos, J. M., Haertlein, M., Ron, D.. 2021-04-20. Structures of a deAMPylation complex rationalise the switch between antagonistic catalytic activities of FICD. https://doi.org/10.1101/2021.04.20.440599

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