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bioRxiv · 10.1101/787770

Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin receptor assemblies

Niemeyer, M.·Moreno Castillo, E.·Ihling, C. H.·Iacobucci, C.·Wilde, V.·Hellmuth, A.·Hoehenwarter, W.·Samodelov, S. L.·Zurbriggen, M. D.·Kastritis, P. L.·Sinz, A.·Calderon Villalobos, L. I. A.
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Abstract

Cullin RING-type E3 ubiquitin ligases SCFTIR1/AFB1-5 and their ubiquitylation targets, AUX/IAAs, sense auxin concentrations in the nucleus. TIR1 binds a surface-exposed degron in AUX/IAAs promoting their ubiquitylation and rapid auxin-regulated proteasomal degradation. Here, we resolved TIR1{middle dot}auxin{middle dot}IAA7 and TIR1{middle dot}auxin{middle dot}IAA12 complex topology, and show that flexible intrinsically disordered regions (IDRs) in the degrons vicinity, cooperatively position AUX/IAAs on TIR1. The AUX/IAA PB1 interaction domain also assists in non-native contacts, affecting AUX/IAA dynamic interaction states. Our results establish a role for IDRs in modulating auxin receptor assemblies. By securing AUX/IAAs on two opposite surfaces of TIR1, IDR diversity supports locally tailored positioning for targeted ubiquitylation, and might provide conformational flexibility for adopting a multiplicity of functional states. We postulate IDRs in distinct members of the AUX/IAA family to be an adaptive signature for protein interaction and initiation region for proteasome recruitment.

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Niemeyer, M., Moreno Castillo, E., Ihling, C. H., Iacobucci, C., Wilde, V., Hellmuth, A., Hoehenwarter, W., Samodelov, S. L., Zurbriggen, M. D., Kastritis, P. L., Sinz, A., Calderon Villalobos, L. I. A.. 2019-09-30. Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin receptor assemblies. https://doi.org/10.1101/787770

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