title: Structural insights into maize viviparous14, a key enzyme in the biosynthesis of the phytohormone abscisic acid.
abstract: The key regulatory step in the biosynthesis of abscisic acid (ABA), a hormone central to the regulation of several important processes in plants, is the oxidative cleavage of the 11,12 double bond of a 9-cis-epoxycarotenoid. The enzyme viviparous14 (VP14) performs this cleavage in maize (Zea mays), making it a target for the rational design of novel chemical agents and genetic modifications that improve plant behavior through the modulation of ABA levels. The structure of VP14, determined to 3.2-Å resolution, provides both insight into the determinants of regio- and stereospecificity of this enzyme and suggests a possible mechanism for oxidative cleavage. Furthermore, mutagenesis of the distantly related CCD1 of maize shows how the VP14 structure represents a template for all plant carotenoid cleavage dioxygenases (CCDs). In addition, the structure suggests how VP14 associates with the membrane as a way of gaining access to its membrane soluble substrate.
authors.affiliation: Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Simon A J
authors.initials: SA
authors.lastname: Messing
authors.forename: Sandra B
authors.initials: SB
authors.lastname: Gabelli
authors.forename: Ignacia
authors.initials: I
authors.lastname: Echeverria
authors.forename: Jonathan T
authors.initials: JT
authors.lastname: Vogel
authors.forename: Jiahn Chou
authors.initials: JC
authors.lastname: Guan
authors.forename: Bao Cai
authors.initials: BC
authors.lastname: Tan
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Klee
authors.forename: Donald R
authors.initials: DR
authors.lastname: McCarty
authors.forename: L Mario
authors.initials: LM
authors.lastname: Amzel
mesh_terms: D000040:Abscisic Acid / Q000096:biosynthesis*; D000595:Amino Acid Sequence; D004252:DNA Mutational Analysis; D049308:Dioxygenases / Q000235:genetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D003313:Zea mays / Q000201:enzymology* / Q000235:genetics
chemical_list: D010940:Plant Proteins; D000040:Abscisic Acid; D049308:Dioxygenases; C431939:carotenoid cleavage dioxygenase 1