title: A novel role for Arabidopsis mitochondrial ABC transporter ATM3 in molybdenum cofactor biosynthesis.
abstract: The molybdenum cofactor (Moco) is a prosthetic group required by a number of enzymes, such as nitrate reductase, sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase. Its biosynthesis in eukaryotes can be divided into four steps, of which the last three are proposed to occur in the cytosol. Here, we report that the mitochondrial ABC transporter ATM3, previously implicated in the maturation of extramitochondrial iron-sulfur proteins, has a crucial role also in Moco biosynthesis. In ATM3 insertion mutants of Arabidopsis thaliana, the activities of nitrate reductase and sulfite oxidase were decreased to approximately 50%, whereas the activities of xanthine dehydrogenase and aldehyde oxidase, whose activities also depend on iron-sulfur clusters, were virtually undetectable. Moreover, atm3 mutants accumulated cyclic pyranopterin monophosphate, the first intermediate of Moco biosynthesis, but showed decreased amounts of Moco. Specific antibodies against the Moco biosynthesis proteins CNX2 and CNX3 showed that the first step of Moco biosynthesis is localized in the mitochondrial matrix. Together with the observation that cyclic pyranopterin monophosphate accumulated in purified mitochondria, particularly in atm3 mutants, our data suggest that mitochondria and the ABC transporter ATM3 have a novel role in the biosynthesis of Moco.
authors.affiliation: Institut für Pflanzenbiologie, Technische Universität Braunschweig, 38023 Braunschweig, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Teschner
authors.forename: Nicole
authors.initials: N
authors.lastname: Lachmann
authors.forename: Jutta
authors.initials: J
authors.lastname: Schulze
authors.forename: Mirco
authors.initials: M
authors.lastname: Geisler
authors.forename: Kristina
authors.initials: K
authors.lastname: Selbach
authors.forename: Jose
authors.initials: J
authors.lastname: Santamaria-Araujo
authors.forename: Janneke
authors.initials: J
authors.lastname: Balk
authors.forename: Ralf R
authors.initials: RR
authors.lastname: Mendel
authors.forename: Florian
authors.initials: F
authors.lastname: Bittner
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000378:metabolism* / Q000502:physiology; D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D003067:Coenzymes / Q000096:biosynthesis*; D055864:Droughts; D008667:Metalloproteins / Q000096:biosynthesis*; D008928:Mitochondria / Q000737:chemistry*; D000090006:Molybdenum Cofactors; D009154:Mutation; D011621:Pteridines
chemical_list: D018528:ATP-Binding Cassette Transporters; D029681:Arabidopsis Proteins; D003067:Coenzymes; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D011621:Pteridines; C522743:ATM1 protein, Arabidopsis; C022261:molybdopterin