A gate-latch-lock mechanism for hormone signalling by abscisic acid receptors.
Abscisic acid (ABA) is a ubiquitous hormone that regulates plant growth, development and responses to environmental stresses. Its action is mediated by the PYR/PYL/RCAR family of START proteins, but it remains unclear how these receptors bind ABA and, in turn, how hormone binding leads to inhibition of the downstream type 2C protein phosphatase (PP2C) effectors. Here we report crystal structures of apo and ABA-bound receptors as well as a ternary PYL2-ABA-PP2C complex. The apo receptors contain an open ligand-binding pocket flanked by a gate that closes in response to ABA by way of conformational changes in two highly conserved beta-loops that serve as a gate and latch. Moreover, ABA-induced closure of the gate creates a surface that enables the receptor to dock into and competitively inhibit the PP2C active site. A conserved tryptophan in the PP2C inserts directly between the gate and latch, which functions to further lock the receptor in a closed conformation. Together, our results identify a conserved gate-latch-lock mechanism underlying ABA signalling.
Melcher
Karsten
K
Laboratory of Structural Sciences, Van Andel Research Institute, 333 Bostwick Avenue, N.E., Grand Rapids, Michigan 49503, USA.
Ng
Ley-Moy
LM
Zhou
X Edward
XE
Soon
Fen-Fen
FF
Xu
Yong
Y
Suino-Powell
Kelly M
KM
Park
Sang-Youl
SY
Weiner
Joshua J
JJ
Fujii
Hiroaki
H
Chinnusamy
Viswanathan
V
Kovach
Amanda
A
Li
Jun
J
Wang
Yonghong
Y
Li
Jiayang
J
Peterson
Francis C
FC
Jensen
Davin R
DR
Yong
Eu-Leong
EL
Volkman
Brian F
BF
Cutler
Sean R
SR
Zhu
Jian-Kang
JK
Xu
H Eric
HE
D000040:Abscisic Acid / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001665:Binding Sites; D004252:DNA Mutational Analysis; D008958:Models, Molecular; D030821:Plants, Genetically Modified; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction / Q000502:physiology*
D029681:Arabidopsis Proteins; D000040:Abscisic Acid