title: Binding of sulfurated molybdenum cofactor to the C-terminal domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration.
abstract: The molybdenum cofactor sulfurase ABA3 from Arabidopsis thaliana is needed for post-translational activation of aldehyde oxidase and xanthine dehydrogenase by transferring a sulfur atom to the desulfo-molybdenum cofactor of these enzymes. ABA3 is a two-domain protein consisting of an NH(2)-terminal NifS-like cysteine desulfurase domain and a C-terminal domain of yet undescribed function. The NH(2)-terminal domain of ABA3 decomposes l-cysteine to yield elemental sulfur, which subsequently is bound as persulfide to a conserved protein cysteinyl residue within this domain. In vivo, activation of aldehyde oxidase and xanthine dehydrogenase also depends on the function of the C-terminal domain, as can be concluded from the A. thaliana aba3/sir3-3 mutant. sir3-3 plants are strongly reduced in aldehyde oxidase and xanthine dehydrogenase activities due to a substitution of arginine 723 by a lysine within the C-terminal domain of the ABA3 protein. Here we present first evidence for the function of the C-terminal domain and show that molybdenum cofactor is bound to this domain with high affinity. Furthermore, cyanide-treated ABA3 C terminus was shown to release thiocyanate, indicating that the molybdenum cofactor bound to the C-terminal domain is present in the sulfurated form. Co-incubation of partially active aldehyde oxidase and xanthine dehydrogenase with ABA3 C terminus carrying sulfurated molybdenum cofactor resulted in stimulation of aldehyde oxidase and xanthine dehydrogenase activity. The data of this work suggest that the C-terminal domain of ABA3 might act as a scaffold protein where prebound desulfo-molybdenum cofactor is converted into sulfurated cofactor prior to activation of aldehyde oxidase and xanthine dehydrogenase.
authors.affiliation: Department of Plant Biology and Department of Environmental Geology, Technical University of Braunschweig, Humboldtstrasse 1, Braunschweig, Germany.
authors.forename: Silke
authors.initials: S
authors.lastname: Wollers
authors.forename: Torsten
authors.initials: T
authors.lastname: Heidenreich
authors.forename: Maryam
authors.initials: M
authors.lastname: Zarepour
authors.forename: Dieter
authors.initials: D
authors.lastname: Zachmann
authors.forename: Claudia
authors.initials: C
authors.lastname: Kraft
authors.forename: Yunde
authors.initials: Y
authors.lastname: Zhao
authors.forename: Ralf R
authors.initials: RR
authors.lastname: Mendel
authors.forename: Florian
authors.initials: F
authors.lastname: Bittner
mesh_terms: D042931:Aldehyde Oxidase / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003067:Coenzymes / Q000378:metabolism*; D003545:Cysteine / Q000378:metabolism; D004789:Enzyme Activation / Q000502:physiology; D008982:Molybdenum / Q000378:metabolism*; D009154:Mutation; D017434:Protein Structure, Tertiary / Q000502:physiology; D013440:Sulfides / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D013466:Sulfurtransferases / Q000235:genetics / Q000378:metabolism*; D014968:Xanthine Dehydrogenase / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D003067:Coenzymes; D013440:Sulfides; C051552:persulfides; D013455:Sulfur; D008982:Molybdenum; D014968:Xanthine Dehydrogenase; D042931:Aldehyde Oxidase; C440026:ABA3 protein, Arabidopsis; D013466:Sulfurtransferases; D003545:Cysteine