PT  - JOURNAL ARTICLE
AU  - Michael Niemeyer
AU  - Elena Moreno Castillo
AU  - Christian H. Ihling
AU  - Claudio Iacobucci
AU  - Verona Wilde
AU  - Antje Hellmuth
AU  - Wolfgang Hoehenwarter
AU  - Sophia L. Samodelov
AU  - Matias D. Zurbriggen
AU  - Panagiotis L. Kastritis
AU  - Andrea Sinz
AU  - Luz Irina A. Calderón Villalobos
TI  - Flexibility of intrinsically disordered degrons in AUX/IAA proteins reinforces auxin receptor assemblies
AID  - 10.1101/787770
DP  - 2019 Jan 01
TA  - bioRxiv
PG  - 787770
4099  - http://biorxiv.org/content/early/2019/09/30/787770.short
4100  - http://biorxiv.org/content/early/2019/09/30/787770.full
AB  - 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·auxin·IAA7 and TIR1·auxin·IAA12 complex topology, and show that flexible intrinsically disordered regions (IDRs) in the degron’s 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.