Biochemical and mass spectrometric evidence for quaternary structure modifications of plant threonine deaminase induced by isoleucine.
Arabidopsis thaliana threonine deaminase (TD) is a tetramer composed of identical approximately 59600 Da subunits. TD activity has been shown to be inhibited by isoleucine. This effect is reversed by a large excess of valine. Nondenaturant gel filtration, polyacrylamide gel electrophoresis, and mass spectrometry experiments demonstrated that binding of isoleucine on TD induces dimerization of the enzyme, whereas tetramerization is restored by addition of a high valine concentration. Nondenaturant gel filtration and electrospray ionization mass spectrometry of the enzyme in the presence of increasing amounts of isoleucine suggest a fast equilibrium between the tetramer and the dimer. Finally, study of TD mutants allowed us to focus on the specific role of each isoleucine-binding site.
Halgand
Frédéric
F
Laboratoire de Spectrométrie de Masse, Institut de Chimie des Substances Naturelles, CNRS, 1 Avenue de la Terrasse, 91198 Gif-sur-Yvette, France. halgand@icsn.cnrs-gif.fr
Wessel
Peter M
PM
Laprévote
Olivier
O
Dumas
Renaud
R
D017360:Arabidopsis / Q000201:enzymology*; D001665:Binding Sites; D002850:Chromatography, Gel; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D015971:Gene Expression Regulation, Enzymologic; D007532:Isoleucine / Q000494:pharmacology*; D013058:Mass Spectrometry; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D013913:Threonine Dehydratase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D014633:Valine / Q000494:pharmacology
D011994:Recombinant Proteins; D007532:Isoleucine; D013913:Threonine Dehydratase; D014633:Valine