1. Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi 464-8601, Japan
2. Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
3. RIKEN Harima Institute at SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 Japan
4. Department of Applied Biological Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
5. These authors contributed equally to this work.

Correspondence to: Hiroaki Kato^2,3Makoto Matsuoka¹ Correspondence and requests for materials should be addressed to H.K. (Email: katohiro@pharm.kyoto-u.ac.jp) or M.M. (Email: makoto@nuagr1.agr.nagoya-u.ac.jp).

Abstract

Gibberellins (GAs) are phytohormones essential for many developmental processes in plants¹. A nuclear GA receptor, GIBBERELLIN INSENSITIVE DWARF1 (GID1), has a primary structure similar to that of the hormone-sensitive lipases (HSLs)^{2, 3}. Here we analyse the crystal structure of Oryza sativa GID1 (OsGID1) bound with GA₄ and GA₃ at 1.9 Å resolution. The overall structure of both complexes shows an /-hydrolase fold similar to that of HSLs except for an amino-terminal lid. The GA-binding pocket corresponds to the substrate-binding site of HSLs. On the basis of the OsGID1 structure, we mutagenized important residues for GA binding and examined their binding activities. Almost all of them showed very little or no activity, confirming that the residues revealed by structural analysis are important for GA binding. The replacement of Ile 133 with Leu or Val—residues corresponding to those of the lycophyte Selaginella moellendorffii GID1s—caused an increase in the binding affinity for GA₃₄, a 2-hydroxylated GA₄. These observations indicate that GID1 originated from HSL and was further modified to have higher affinity and more strict selectivity for bioactive GAs by adapting the amino acids involved in GA binding in the course of plant evolution.

1. Bioscience and Biotechnology Center, Nagoya University, Nagoya, Aichi 464-8601, Japan
2. Department of Structural Biology, Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida Shimoadachi-cho, Sakyo-ku, Kyoto 606-8501, Japan
3. RIKEN Harima Institute at SPring-8, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148 Japan
4. Department of Applied Biological Chemistry, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan
5. These authors contributed equally to this work.

Correspondence to: Hiroaki Kato^2,3Makoto Matsuoka¹ Correspondence and requests for materials should be addressed to H.K. (Email: katohiro@pharm.kyoto-u.ac.jp) or M.M. (Email: makoto@nuagr1.agr.nagoya-u.ac.jp).

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