Structural Basis for Prereceptor Modulation of Plant Hormones by GH3 Proteins.

LIGASES; PLANT hormones; PLANT enzymes; BENZOATES; JASMONIC acid; AMINO acid content of plants

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-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 carboxyl-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 adaptab|e three-dimensional scaffold is used for the evolution of promiscuous activity across an enzyme family for modulation of plant signaling molecules. [ABSTRACT FROM AUTHOR]

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