Crystal structure of Arabidopsis thaliana 12-oxophytodienoate reductase isoform 3 in complex with 8-iso prostaglandin A(1)

12-Oxophytodienoate reductase 3 (OPR3), one of the enzymes involved in the biosynthesis of the plant hormone jasmonic acid (JA), catalyzes the reduction of the cyclopentenone ring of (9S,13S)-12-oxophytodienoate [(9S,13S)-OPDA]. However, there has been no structural information about the interaction between OPRs and the physiologically relevant (9S,13S)-OPDA. Here we report the crystal structure of Arabidopsis thaliana OPR3 in complex with 8-iso prostaglandin A1 (8-iso PGA₁) which has the same stereochemistry in the cyclopentenone ring as in the physiologically relevant 9S,13S-OPDA. This structure reveals a new binding mode for substrate that likely contributes to the relaxed stereospecificity observed for AtOPR3.