title: NADP-malate dehydrogenase from unicellular green alga Chlamydomonas reinhardtii. A first step toward redox regulation?
abstract: The determinants of the thioredoxin (TRX)-dependent redox regulation of the chloroplastic NADP-malate dehydrogenase (NADP-MDH) from the eukaryotic green alga Chlamydomonas reinhardtii have been investigated using site-directed mutagenesis. The results indicate that a single C-terminal disulfide is responsible for this regulation. The redox midpoint potential of this disulfide is less negative than that of the higher plant enzyme. The regulation is of an all-or-nothing type, lacking the fine-tuning provided by the second N-terminal disulfide found only in NADP-MDH from higher plants. The decreased stability of specific cysteine/alanine mutants is consistent with the presence of a structural disulfide formed by two cysteine residues that are not involved in regulation of activity. Measurements of the ability of C. reinhardtii thioredoxin f (TRX f) to activate wild-type and site-directed mutants of sorghum (Sorghum vulgare) NADP-MDH suggest that the algal TRX f has a redox midpoint potential that is less negative than most those of higher plant TRXs f. These results are discussed from an evolutionary point of view.
authors.affiliation: Institut de Biotechnologie des Plantes, Unité Mixte de Recherche 8618 Centre National de la Recherche Scientifique, Université Paris-Sud, 91405 Orsay cedex, France.
authors.forename: Stéphane D
authors.initials: SD
authors.lastname: Lemaire
authors.forename: Alberto
authors.initials: A
authors.lastname: Quesada
authors.forename: Faustino
authors.initials: F
authors.lastname: Merchan
authors.forename: Juan Manuel
authors.initials: JM
authors.lastname: Corral
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Igeno
authors.forename: Eliane
authors.initials: E
authors.lastname: Keryer
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Issakidis-Bourguet
authors.forename: Masakazu
authors.initials: M
authors.lastname: Hirasawa
authors.forename: David B
authors.initials: DB
authors.lastname: Knaff
authors.forename: Myroslawa
authors.initials: M
authors.lastname: Miginiac-Maslow
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000201:enzymology*; D004789:Enzyme Activation; D004795:Enzyme Stability; D015870:Gene Expression; D008291:Malate Dehydrogenase / Q000737:chemistry / Q000378:metabolism*; D050538:Malate Dehydrogenase (NADP+); D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D011487:Protein Conformation; D013997:Time Factors
chemical_list: D008291:Malate Dehydrogenase; D050538:Malate Dehydrogenase (NADP+)