title: Lupinus luteus pathogenesis-related protein as a reservoir for cytokinin.
abstract: Plant pathogenesis-related (PR) proteins of class 10 (PR-10) are small and cytosolic. The main feature of their three-dimensional structure is a large cavity between a seven-stranded antiparallel beta-sheet and a long C-terminal alpha-helix. Although PR-10 proteins are abundant in plants, their physiological role remains unknown. Recent data have indicated ligand binding as their possible biological function. The article describes the structure of a complex between a classic PR-10 protein (yellow lupine LlPR-10.2B) and the plant hormone, trans-zeatin. Previously, trans-zeatin binding has been reported in a structurally related cytokinin-specific binding protein, which has a distant sequence relation with classic PR-10 proteins. In the present 1.35 A resolution crystallographic model, three perfectly ordered zeatin molecules are found in the binding cavity of the protein. The fact that three zeatin molecules are bound by the protein when only a fourfold molar excess of the ligand was used indicates an unusual type of affinity for this ligand and suggests that LlPR-10.2B, and perhaps other PR-10 proteins as well, acts as a reservoir of cytokinin molecules in the aqueous environment of the cell.
authors.affiliation: Center for Biocrystallographic Research, Institute of Bioorganic Chemistry, Polish Academy of Sciences, 61-704 Poznan, Poland.
authors.forename: Humberto
authors.initials: H
authors.lastname: Fernandes
authors.forename: Oliwia
authors.initials: O
authors.lastname: Pasternak
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Bujacz
authors.forename: Anna
authors.initials: A
authors.lastname: Bujacz
authors.forename: Michal M
authors.initials: MM
authors.lastname: Sikorski
authors.forename: Mariusz
authors.initials: M
authors.lastname: Jaskolski
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003583:Cytokinins / Q000737:chemistry / Q000378:metabolism*; D031297:Lupinus / Q000737:chemistry*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D010937:Plant Growth Regulators / Q000737:chemistry* / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D015026:Zeatin / Q000737:chemistry* / Q000378:metabolism
chemical_list: D003583:Cytokinins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C053376:pathogenesis-related proteins, plant; D015026:Zeatin