title: Twin anchors of the soybean isoflavonoid metabolon: evidence for tethering of the complex to the endoplasmic reticulum by IFS and C4H.
abstract: Isoflavonoids are specialized plant metabolites, almost exclusive to legumes, and their biosynthesis forms a branch of the diverse phenylpropanoid pathway. Plant metabolism may be coordinated at many levels, including formation of protein complexes, or 'metabolons', which represent the molecular level of organization. Here, we have confirmed the existence of the long-postulated isoflavonoid metabolon by identifying elements of the complex, their subcellular localizations and their interactions. Isoflavone synthase (IFS) and cinnamate 4-hydroxylase (C4H) have been shown to be tandem P450 enzymes that are anchored in the ER, interacting with soluble enzymes of the phenylpropanoid and isoflavonoid pathways (chalcone synthase, chalcone reductase and chalcone isomerase). The soluble enzymes of these pathways, whether localized to the cytoplasm or nucleus, are tethered to the ER through interaction with these P450s. The complex is also held together by interactions between the soluble elements. We provide evidence for IFS interaction with upstream and non-consecutive enzymes. The existence of such a protein complex suggests a possible mechanism for flux of metabolites into the isoflavonoid pathway. Further, through interaction studies, we identified several candidates that are associated with GmIFS2, an isoform of IFS, in soybean hairy roots. This list provides additional candidates for various biosynthetic and structural elements that are involved in isoflavonoid production. Our interaction studies provide valuable information about isoform specificity among isoflavonoid enzymes, which may guide future engineering of the pathway in legumes or help overcome bottlenecks in heterologous expression.
authors: Department of Biology, University of Western Ontario, London, Ontario, Canada.|Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, Canada.
authors: Mehran
authors: M
authors: Dastmalchi
authors: Department of Biology, University of Western Ontario, London, Ontario, Canada.
authors: Mark A
authors: MA
authors: Bernards
authors: Department of Biology, University of Western Ontario, London, Ontario, Canada.|Agriculture and Agri-Food Canada, 1391 Sandford Street, London, Ontario, Canada.
authors: Sangeeta
authors: S
authors: Dhaubhadel
mesh_terms: D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000378:metabolism; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D019753:Intramolecular Lyases / Q000235:genetics / Q000378:metabolism; D007529:Isoflavones / Q000378:metabolism*; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D030821:Plants, Genetically Modified; D025941:Protein Interaction Mapping / Q000379:methods; D020033:Protein Isoforms; D013025:Glycine max / Q000235:genetics / Q000378:metabolism*; D050564:Trans-Cinnamate 4-Monooxygenase / Q000235:genetics / Q000378:metabolism*
chemical_list: D007529:Isoflavones; D010940:Plant Proteins; D020033:Protein Isoforms; D003577:Cytochrome P-450 Enzyme System; D000429:Alcohol Oxidoreductases; C093070:chalcone reductase; D010105:Oxygenases; C048489:isoflavone synthase; D050564:Trans-Cinnamate 4-Monooxygenase; D019753:Intramolecular Lyases; C019865:chalcone isomerase
keywords: isoflavonoids; isoform specificity; metabolon; protein-protein interaction; soybean; specialized metabolism