Primary citation
Title Structures of Michaelis and Product Complexes of Plant Cytokinin Dehydrogenase: Implications for Flavoenzyme Catalysis
Authors Malito,; Coda,; Bilyeu,; Fraaije,; Mattevi,
Journal vol:341, pag:1237 (2004), Identifiers: PubMed ID (15321719)search DOI (10.1016/j.jmb.2004.06.083)
Abstract Cytokinins form a diverse class of compounds that are essential for plant growth. Cytokinin dehydrogenase has a major role in the control of the levels of these plant hormones by catalysing their irreversible oxidation. The crystal structure of Zea mays cytokinin dehydrogenase displays the same two-domain topology of the flavoenzymes of the vanillyl-alcohol oxidase family but its active site cannot be related to that of any other family member. The X-ray analysis reveals a bipartite architecture of the catalytic centre, which consists of a funnel-shaped region on the protein surface and an internal cavity lined by the flavin ring. A pore with diameter of about 4A connects the two active-site regions. Snapshots of two critical steps along the reaction cycle were obtained through the structural analysis of the complexes with a slowly reacting substrate and the reaction product, which correspond to the states immediately before (Michaelis complex) and after (product complex) oxidation has taken place. The substrate displays a "plug-into-socket" binding mode that seals the catalytic site and precisely positions the carbon atom undergoing oxidation in close contact with the reactive locus of the flavin. A polarising H-bond between the substrate amine group and an Asp-Glu pair may facilitate oxidation. Substrate to product conversion results in small atomic movements, which lead to a planar conformation of the reaction product allowing double-bond conjugation. These features in the mechanism of amine recognition and oxidation differ from those observed in other flavin-dependent amine oxidases.
MeSH terms Adeninesearch, Binding Sitessearch, Crystallographysearch, X-Raysearch, Cytokininssearch, Flavin-Adenine Dinucleotidesearch, Modelssearch, Molecularsearch, Molecular Structuresearch, Oxidation-Reductionsearch, Oxidoreductasessearch, Plant Proteinssearch, Protein Bindingsearch, Protein Structuresearch, Tertiarysearch, Zea mayssearch, Zeatinsearch
Other entries described in this publication 1w1q, 1w1s, 1w1r