 |
PDBsum entry 2p1n
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Signaling protein
|
PDB id
|
|
|
|
2p1n
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
 |
Contents |
 |
|
|
|
|
|
|
|
|
|
|
|
126 a.a.
|
|
|
|
|
|
|
|
|
|
|
571 a.a.
|
|
|
|
|
|
|
|
|
|
|
13 a.a.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
References listed in PDB file
|
|
|
Key reference
|
|
|
Title
|
|
Mechanism of auxin perception by the tir1 ubiquitin ligase.
|
|
|
Authors
|
|
X.Tan,
L.I.Calderon-Villalobos,
M.Sharon,
C.Zheng,
C.V.Robinson,
M.Estelle,
N.Zheng.
|
|
|
Ref.
|
|
Nature, 2007,
446,
640-645.
[DOI no: ]
|
|
|
PubMed id
|
|
|
|
|
|
Abstract
|
|
|
Auxin is a pivotal plant hormone that controls many aspects of plant growth and
development. Perceived by a small family of F-box proteins including transport
inhibitor response 1 (TIR1), auxin regulates gene expression by promoting SCF
ubiquitin-ligase-catalysed degradation of the Aux/IAA transcription repressors,
but how the TIR1 F-box protein senses and becomes activated by auxin remains
unclear. Here we present the crystal structures of the Arabidopsis TIR1-ASK1
complex, free and in complexes with three different auxin compounds and an
Aux/IAA substrate peptide. These structures show that the leucine-rich repeat
domain of TIR1 contains an unexpected inositol hexakisphosphate co-factor and
recognizes auxin and the Aux/IAA polypeptide substrate through a single surface
pocket. Anchored to the base of the TIR1 pocket, auxin binds to a partially
promiscuous site, which can also accommodate various auxin analogues. Docked on
top of auxin, the Aux/IAA substrate peptide occupies the rest of the TIR1 pocket
and completely encloses the hormone-binding site. By filling in a hydrophobic
cavity at the protein interface, auxin enhances the TIR1-substrate interactions
by acting as a 'molecular glue'. Our results establish the first structural
model of a plant hormone receptor.
|
|
|
|
|
|
|
|
Figure 1.
Figure 1: Crystal structure of the TIR1–ASK1 complex with
auxin and the IAA7 degron peptide. a, b, Two views of the
complex structure are shown as a ribbon diagram. TIR1, ASK1 and
the IAA7 substrate peptide are coloured grey, blue and orange,
respectively. The F-box and LRR domains of TIR1 are labelled.
Auxin is represented by a space-filling model (CPK). The InsP[6]
molecule is shown as a stick model.
|
|
Figure 6.
Figure 6: A model of auxin-regulated TIR1–substrate
interactions. A schematic diagram of auxin functioning
as a 'molecular glue' to enhance TIR1–substrate interactions.
In contrast to an allosteric mechanism, auxin binds to the same
TIR1 pocket that docks the Aux/IAA substrate. Without inducing
significant conformational changes in its receptor, auxin
increases the affinity of two proteins by simultaneously
interacting with both in a cavity at the protein interface.
|
|
|
|
|
|
The above figures are
reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2007,
446,
640-645)
copyright 2007.
|
|
|
|
|
|
|
