title: Crystal structure of 12-oxophytodienoate reductase 3 from tomato: self-inhibition by dimerization.
abstract: 12-Oxophytodienoate reductase (OPR) 3, a homologue of old yellow enzyme (OYE), catalyzes the reduction of 9S,13S-12-oxophytodienoate to the corresponding cyclopentanone, which is subsequently converted to the plant hormone jasmonic acid (JA). JA and JA derivatives, as well as 12-oxophytodienoate and related cyclopentenones, are known to regulate gene expression in plant development and defense. Together with other oxygenated fatty acid derivatives, they form the oxylipin signature in plants, which resembles the pool of prostaglandins in animals. Here, we report the crystal structure of OPR3 from tomato and of two OPR3 mutants. Although the catalytic residues of OPR3 and related OYEs are highly conserved, several characteristic differences can be discerned in the substrate-binding regions, explaining the remarkable substrate stereoselectivity of OPR isozymes. Interestingly, OPR3 crystallized as an extraordinary self-inhibited dimer. Mutagenesis studies and biochemical analysis confirmed a weak dimerization of OPR3 in vitro, which correlated with a loss of enzymatic activity. Based on structural data of OPR3, a putative mechanism for a strong and reversible dimerization of OPR3 in vivo that involves phosphorylation of OPR3 is suggested. This mechanism could contribute to the shaping of the oxylipin signature, which is critical for fine-tuning gene expression in plants.
authors.affiliation: Abteilung Strukturforschung, Max-Planck-Institut für Biochemie, 82152 Martinsried, Germany. constanze.breithaupt@sbg.ac.at
authors.forename: Constanze
authors.initials: C
authors.lastname: Breithaupt
authors.forename: Robert
authors.initials: R
authors.lastname: Kurzbauer
authors.forename: Hauke
authors.initials: H
authors.lastname: Lilie
authors.forename: Andreas
authors.initials: A
authors.lastname: Schaller
authors.forename: Jochen
authors.initials: J
authors.lastname: Strassner
authors.forename: Robert
authors.initials: R
authors.lastname: Huber
authors.forename: Peter
authors.initials: P
authors.lastname: Macheroux
authors.forename: Tim
authors.initials: T
authors.lastname: Clausen
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D018551:Solanum lycopersicum / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000737:chemistry* / Q000378:metabolism*; D017433:Protein Structure, Secondary; D013329:Structure-Activity Relationship
chemical_list: D044925:Oxidoreductases Acting on CH-CH Group Donors; C106360:12-oxophytodienoate reductase