A Gate-Latch-Lock Mechanism for Hormone Signaling by Abscisic Acid Receptors

By K. Melcher, L. Ng, X. E. Zhou, F.-F. Soon, Yong Xu, K. Suino-Powell, Sang-Youl Park, Joshua J. Weiner, Hiroaki Fujii, V. Chinnusamy and 11 more. Nature, 2009

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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 β-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.

Subfields: Physiology, Plant Science

View Paper: https://www.semanticscholar.org/paper/79d74292f23e90caabd82ba627b954550592482c

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Citations in the corpus

Photosynthesis under stressful environments: An overview (2013, background): “ABA is usually known as a stress hormone due to its high accumulation under stress environments (Kempa et al. 2008, Melcher et al. 2009).”
Abiotic stress signaling and responses in plants (2016, background): “In turn, ABI1 and the other PP2Cs protect the GTP exchange factor RopGEF1 from ABA-induced degradation, thus forming a RopGEF-ROP-PP2C control loop that may counteract leaky ABA signaling by monomeric PYLs in the absence of stress (Li et al., 2016).”
Comprehending crystalline β-carotene accumulation by comparing engineered cell models and the natural carotenoid-rich system of citrus (2011, neutral): “SMF and MntH , NRAMP homologues in yeast and bacteria, respectively, are involved in manganese (Mn) accumulation (Makui et al. , 2000; Portnoy et al. , 2000).”
ABA signal transduction at the crossroad of biotic and abiotic stress responses. (2012, background): “Additionally, the tryptophan residue of PP2C stabilizes this ABA-PYR/PYLs-PP2C complex and makes contact with ABA (Melcher et al. 2009; Miyazono et al. 2009; Yin et al. 2009).”
Early abscisic acid signal transduction mechanisms: newly discovered components and newly emerging questions. (2010, background): “, PYR1 P88, R116) also reduce ABA sensitivity (Melcher et al. 2009; Miyazono et al. 2009; Nishimura et al. 2009; Park et al. 2009; Yin et al. 2009), underlining the importance of these loops for ABA binding and receptor function.”
Guard Cell Signal Transduction Network: Advances in Understanding Abscisic Acid, CO2, and Ca2+ Signaling (2010, background): “F or p er so na l u se o nl y. ANRV410-PP61-24 ARI 31 March 2010 19:9 ABA ABA receptors OST1/SnRK2s CPK3/4/6/11 GCA2 RbohD/F-ROS Prime/enhance stomatal closing Ca2+ sensitivity AtMRP5 Stomatal closure SLAC1-S-type anion channel R-type anion channel Regulation of other ion channels, pumps, and metabo”
Plant abiotic stress response and nutrient use efficiency (2020, background): “It is now well accepted that PYR/PYL/RCAR proteins, PP2Cs and SnRK2 kinases constitute the core ABA signaling module that is responsible for the earliest events of ABA signaling.”
ABA signaling in stress-response and seed development (2013, background): “…complex and the structural mechanism of PP2C inhibition that underlies the regulation of phosphorylation signaling in plant stress responses and seed developmental processes by ABA sensing (Melcher et al. 2009; Miyazono et al. 2009; Nishimura et al. 2009; Santiago et al. 2009; Yin et al. 2009).”
Recent Advances in Photosynthesis Under Drought and Salinity (2011, background): “Recently, a series of crystallographic studies have clearly demonstrated that interaction of PP2C with the hydrophobic surface of ABA-bound receptors inhibits PP2C activity (Melcher et al., 2009; Miyazono et al., 2009; Yin et al., 2009).”
Molecular Basis of the Core Regulatory Network in ABA Responses: Sensing, Signaling and Transport (2010, background): “In contrast, PP2C refi nes the closed conformation of the ABA-bound receptor by assisting with ABA loading into the receptor, which allows the gate loop of the receptor to bind to the active site of PP2C ( Melcher et al. 2009 , Miyazono et al. 2009 , Yin et al. 2009 ).”