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Structural Basis for Prereceptor Modulation of Plant Hormones by GH3 Proteins

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Science  24 May 2012:
1221863
DOI: 10.1126/science.1221863

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Abstract

Acyl acid amido synthetases of the GH3 family act as critical prereceptor modulators of plant hormone action; however, the molecular basis for their hormone selectivity is unclear. Here, we report the crystal structures of benzoate-specific Arabidopsis thaliana AtGH3.12/PBS3 and jasmonic acid (JA)–specific AtGH3.11/JAR1. These structures, combined with biochemical analysis, define features for the conjugation of amino acids to diverse acyl acid substrates and highlight the importance of conformational changes in the C-terminal domain for catalysis. We also identify residues forming the acyl acid binding site across the GH3 family and residues critical for amino acid recognition. Our results demonstrate how a highly adaptable three-dimensional scaffold is used for the evolution of promiscuous activity across an enzyme family for modulation of plant signaling molecules.

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