Structural basis for selective activation of ABA receptors.
Changing environmental conditions and lessening fresh water supplies have sparked intense interest in understanding and manipulating abscisic acid (ABA) signaling, which controls adaptive responses to drought and other abiotic stressors. We recently discovered a selective ABA agonist, pyrabactin, and used it to discover its primary target PYR1, the founding member of the PYR/PYL family of soluble ABA receptors. To understand pyrabactin's selectivity, we have taken a combined structural, chemical and genetic approach. We show that subtle differences between receptor binding pockets control ligand orientation between productive and nonproductive modes. Nonproductive binding occurs without gate closure and prevents receptor activation. Observations in solution show that these orientations are in rapid equilibrium that can be shifted by mutations to control maximal agonist activity. Our results provide a robust framework for the design of new agonists and reveal a new mechanism for agonist selectivity.
Peterson
Francis C
FC
Department of Biochemistry and Center for Eukaryotic Structural Genomics, Medical College of Wisconsin, Milwaukee, Wisconsin, USA.
Burgie
E Sethe
ES
Park
Sang-Youl
SY
Jensen
Davin R
DR
Weiner
Joshua J
JJ
Bingman
Craig A
CA
Chang
Chia-En A
CE
Cutler
Sean R
SR
Phillips
George N
GN
Volkman
Brian F
BF
D017360:Arabidopsis / Q000737:chemistry* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D009281:Naphthalenes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013449:Sulfonamides / Q000737:chemistry
D029681:Arabidopsis Proteins; D026901:Membrane Transport Proteins; D009281:Naphthalenes; C540976:AT4G17870 protein, Arabidopsis; D013449:Sulfonamides; C540973:pyrabactin