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Biochemical characterization of TASSELSEED 2, an essential plant short‐chain dehydrogenase/reductase with broad spectrum activities
Author(s) -
Wu Xiaoqiu,
Knapp Stefan,
Stamp Anna,
Stammers David K.,
Jörnvall Hans,
Dellaporta Stephen L.,
Oppermann Udo
Publication year - 2007
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2007.05642.x
Subject(s) - nad+ kinase , reductase , biochemistry , biology , dehydrogenase , enzyme , complementary dna , stereochemistry , gene , chemistry
The development of unisexual flowers in maize and other plants proceeds through selective elimination of floral organs in an initially bisexual floral meristem. The essential character of the tasselseed 2 gene ( TS2 ) in this cell‐death pathway has been established previously. Molecular cloning of TS2 reveals membership to the evolutionarily conserved superfamily of short‐chain dehydrogenases/reductases, but its substrate specificity remained unknown. Recombinant TS2 protein was produced in Escherichia coli , and purified to apparent homogeneity. Analytical ultracentrifugation and gel filtration experiments show that TS2 is a tetrameric enzyme. Thermal denaturation followed by circular dichroism spectroscopy reveals that TS2 binds NAD(H) and NAD(P)(H). Substrate screening demonstrates that TS2 converts steroids with specificities found at positions 3 and 17, and several dicarbonyl and quinone compounds, thus establishing TS2 as a plant 3β/17β‐hydroxysteroid dehydrogenase and carbonyl/quinone reductase. Taken together, the genetic data and the substrate specificities determined suggest that TS2 converts specific plant compounds and acts as a prereceptor control mechanism, in a manner similar to that of mammalian hydroxysteroid dehydrogenases.