title: Structural basis of unique ligand specificity of KAI2-like protein from parasitic weed Striga hermonthica.
abstract: The perception of two plant germination inducers, karrikins and strigolactones, are mediated by the proteins KAI2 and D14. Recently, KAI2-type proteins from parasitic weeds, which are possibly related to seed germination induced by strigolactone, have been classified into three clades characterized by different responses to karrikin/strigolactone. Here we characterized a karrikin-binding protein in Striga (ShKAI2iB) that belongs to intermediate-evolving KAI2 and provided the structural bases for its karrikin-binding specificity. Binding assays showed that ShKAI2iB bound karrikins but not strigolactone, differing from other KAI2 and D14. The crystal structures of ShKAI2iB and ShKAI2iB-karrikin complex revealed obvious structural differences in a helix located at the entry of its ligand-binding cavity. This results in a smaller closed pocket, which is also the major cause of ShKAI2iB's specificity of binding karrikin. Our structural study also revealed that a few non-conserved amino acids led to the distinct ligand-binding profile of ShKAI2iB, suggesting that the evolution of KAI2 resulted in its diverse functions.
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Yuqun
authors: Y
authors: Xu
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Takuya
authors: T
authors: Miyakawa
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Hidemitsu
authors: H
authors: Nakamura
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Akira
authors: A
authors: Nakamura
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Yusaku
authors: Y
authors: Imamura
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.|JST, CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.|Department of Biochemistry, King Abdulaziz University, Jeddah 21589, Saudi Arabia.
authors: Tadao
authors: T
authors: Asami
authors: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors: Masaru
authors: M
authors: Tanokura
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D019143:Evolution, Molecular; D005663:Furans / Q000378:metabolism*; D006867:Hydrolases / Q000737:chemistry* / Q000378:metabolism*; D007783:Lactones / Q000378:metabolism; D008958:Models, Molecular; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D000072417:Protein Domains; D017433:Protein Structure, Secondary; D034362:Striga / Q000737:chemistry / Q000201:enzymology*; D013379:Substrate Specificity
chemical_list: D005663:Furans; D007783:Lactones; D010940:Plant Proteins; D006867:Hydrolases