1w1r
|
PLANT CYTOKININ DEHYDROGENASE IN COMPLEX WITH TRANS-ZEATIN
OverviewOverview
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.
About this StructureAbout this Structure
1W1R is a Single protein structure of sequence from Zea mays with NAG, FAD and ZEA as ligands. Active as Cytokinin dehydrogenase, with EC number 1.5.99.12 Structure known Active Site: AC1. Full crystallographic information is available from OCA.
ReferenceReference
Structures of Michaelis and product complexes of plant cytokinin dehydrogenase: implications for flavoenzyme catalysis., Malito E, Coda A, Bilyeu KD, Fraaije MW, Mattevi A, J Mol Biol. 2004 Aug 27;341(5):1237-49. PMID:15321719
Page seeded by OCA on Mon Nov 5 17:22:33 2007