tailieunhanh - Báo cáo khoa học: Biochemical characterization of TASSELSEED 2, an essential plant short-chain dehydrogenase ⁄reductase with broad spectrum activities

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 thetasselseed 2 gene (TS2) in this cell-death pathway has been established previously. | ễFEBS Journal Biochemical characterization of TASSELSEED 2 an essential plant short-chain dehydrogenase reductase with broad spectrum activities Xiaoqiu Wu1 Stefan Knapp2 Anna Stamp3 David K. Stammers3 Hans Jornvall1 Stephen L. Dellaporta4 and Udo Oppermann1 1 Department of MedicalBiochemistry and Biophysics Karolinska Institutet Stockholm Sweden 2 StructuralGenomics Consortium University of Oxford Botnar Research Centre UK 3 Division of StructuralBiology The Wellcome Trust Centre for Human Genetics University of Oxford UK 4 Department of Molecular Cellular and DevelopmentalBiology Yale University New Haven CT USA Keywords hydroxysteroid dehydrogenase prereceptor control sex determination short-chain dehydrogenases reductases steroid metabolism Correspondence U. Oppermann StructuralGenomics Consortium University of Oxford Botnar Research Centre Oxford OX3 7LD UK Fax 44 1865 737231 Tel 44 1865 737839 E-mail Present address StructuralGenomics Consortium University of Oxford Botnar Research Centre Oxford UK Received 28 June 2006 revised 3 November 2006 accepted 11 December 2006 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 celldeath pathway has been established previously. Molecular cloning of TS2 reveals membership to the evolutionarily conserved superfamily of shortchain 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 .