Crystal structure of the indole-3-acetic acid-catabolizing enzyme DAO1 from Arabidopsis thaliana

• Published in: Journal of structural biology 2020-12, Vol.212 (3), p.107632-107632, Article 107632
• Main Authors: Jin, So-Hee, Lee, Haehee, Shin, Yongho, Kim, Jeong-Han, Rhee, Sangkee
• Format: Article
• Language: English
• Subjects: AtDAO1; Auxin homeostasis; Crystal structure; Dioxygenase; IAA catabolism
• ISSN: 1047-8477; 1095-8657
• DOI: 10.1016/j.jsb.2020.107632

[Display omitted] •Structure of AtDAO1 and its complex with a cosubstrate 2-oxoglutarate are determined.•AtDAO1 is structurally homologous with members of the 2ODO oxygenase family.•The cosubstrate- and metal-binding site is highly conserved in the 2ODO family.•DAO-specific residues could account for the substrate specificity of AtDAO1 toward IAA. Indole-3-acetic acid (IAA), the major form of the plant hormone auxin, regulates almost every aspect of plant growth and development. Therefore, auxin homeostasis is an essential process in plants. Different metabolic routes are involved in auxin homeostasis, but the catabolic pathway has remained elusive until recent studies identified DIOXYGENASE FOR AUXIN OXIDATION (DAO) from rice and Arabidopsis thaliana. DAO, a member of the 2-oxoglutarate/Fe(II)-dependent oxygenase (2ODO) family, constitutes a major enzyme for IAA catabolism. This enzyme catalyzes, with the cosubstrate 2-oxoglutarate, the conversion of IAA into 2-oxoindole-3-acetic acid, a functionally inactive oxidative product of IAA. Here, we report a crystal structure of the unliganded DAO1 from A. thaliana (AtDAO1) and its complex with 2-oxoglutarate. AtDAO1 is structurally homologous with members of the 2ODO family but exhibits unique features in the prime substrate IAA binding site. We provide structural analyses of a putative binding site for IAA, supporting possible structural determinants for the substrate specificity of AtDAO1 toward IAA.