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Plant Cell. 2010 Sep;22(9):2970-80. doi: 10.1105/tpc.110.074815. Epub 2010 Sep 30.

Structural insights into maize viviparous14, a key enzyme in the biosynthesis of the phytohormone abscisic acid.

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  • 1Department of Biophysics and Biophysical Chemistry, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21205, USA.


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.

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