Crystal structure of 12-oxophytodienoate reductase 3 from tomato: Self-inhibition by dimerization

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 103; no. 39; pp. 14337 - 14342
• Main Authors: Breithaupt, C, Kurzbauer, R, Lilie, H, Schaller, A, Strassner, J, Huber, R, Macheroux, P, Clausen, T
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 26.09.2006; National Acad Sciences
• Subjects: 12-oxophytodienoate reductase; Active sites; Amino Acid Sequence; Amino acids; Binding Sites; Biological Sciences; Catalysis; Crystal structure; Crystallography, X-Ray; Crystals; Dimerization; Dimers; enzyme activity; Enzymes; Gene expression; Models, Molecular; Molecular Sequence Data; Monomers; mutants; Mutation; oxidoreductases; Oxidoreductases Acting on CH-CH Group Donors - chemistry; Oxidoreductases Acting on CH-CH Group Donors - metabolism; Plant growth; Protein Structure, Secondary; Protein subunits; Proteins; Solanum lycopersicum - enzymology; Solanum lycopersicum var. lycopersicum; Structure-Activity Relationship; tomatoes
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0606603103

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.