title: Characterization of the NifS-like domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration.
abstract: The molybdenum cofactor sulfurase ABA3 from Arabidopsis thaliana specifically regulates the activity of the molybdenum enzymes aldehyde oxidase and xanthine dehydrogenase by converting their molybdenum cofactor from the desulfo-form into the sulfo-form. ABA3 is a two-domain protein with an NH2-terminal domain sharing significant similarities to NifS proteins that catalyze the decomposition of l-cysteine to l-alanine and elemental sulfur for iron-sulfur cluster synthesis. Although different in its physiological function, the mechanism of ABA3 for sulfur mobilization was found to be similar to NifS proteins. The protein binds a pyridoxal phosphate cofactor and a substrate-derived persulfide intermediate, and site-directed mutagenesis of strictly conserved binding sites for the cofactor and the persulfide demonstrated that they are essential for molybdenum cofactor sulfurase activity. In vitro, the NifS-like domain of ABA3 activates aldehyde oxidase and xanthine dehydrogenase in the absence of the C-terminal domain, but in vivo, the C-terminal domain is required for proper activation of both target enzymes. In addition to its cysteine desulfurase activity, ABA3-NifS also exhibits selenocysteine lyase activity. Although l-selenocysteine is unlikely to be a natural substrate for ABA3, it is decomposed more efficiently than l-cysteine. Besides mitochondrial AtNFS1 and plastidial AtNFS2, which are both proposed to be involved in iron-sulfur cluster formation, ABA3 is proposed to be a third and cytosolic NifS-like cysteine desulfurase in A. thaliana. However, the sulfur transferase activity of ABA3 is used for post-translational activation of molybdenum enzymes rather than for iron-sulfur cluster assembly.
authors.affiliation: Department of Plant Biology, Technical University of Braunschweig, 38023 Braunschweig, Germany.
authors.forename: Torsten
authors.initials: T
authors.lastname: Heidenreich
authors.forename: Silke
authors.initials: S
authors.lastname: Wollers
authors.forename: Ralf R
authors.initials: RR
authors.lastname: Mendel
authors.forename: Florian
authors.initials: F
authors.lastname: Bittner
mesh_terms: D042931:Aldehyde Oxidase / Q000378:metabolism; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D002384:Catalysis; D003067:Coenzymes / Q000737:chemistry*; D003545:Cysteine / Q000737:chemistry; D003600:Cytosol / Q000737:chemistry; D005456:Fluorescent Dyes / Q000494:pharmacology; D005822:Genetic Vectors; D007506:Iron-Sulfur Proteins / Q000737:chemistry; D007700:Kinetics; D008190:Lyases / Q000737:chemistry; D008239:Lysine / Q000737:chemistry; D008667:Metalloproteins / Q000737:chemistry*; D008982:Molybdenum / Q000737:chemistry*; D000090006:Molybdenum Cofactors; D016297:Mutagenesis, Site-Directed; D009282:Naphthalenesulfonates / Q000494:pharmacology; D010843:Pichia / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011621:Pteridines / Q000737:chemistry*; D011732:Pyridoxal Phosphate / Q000737:chemistry; D017279:Selenocysteine / Q000737:chemistry; D013053:Spectrophotometry; D013379:Substrate Specificity; D013440:Sulfides / Q000737:chemistry; D013466:Sulfurtransferases / Q000737:chemistry* / Q000378:metabolism; D014968:Xanthine Dehydrogenase / Q000378:metabolism
chemical_list: D042931:Aldehyde Oxidase; D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D003067:Coenzymes; D003545:Cysteine; D005456:Fluorescent Dyes; D007506:Iron-Sulfur Proteins; D008190:Lyases; D008239:Lysine; D008667:Metalloproteins; D008982:Molybdenum; D000090006:Molybdenum Cofactors; D009282:Naphthalenesulfonates; D010940:Plant Proteins; D011621:Pteridines; D011732:Pyridoxal Phosphate; D017279:Selenocysteine; D013440:Sulfides; D013466:Sulfurtransferases; D014968:Xanthine Dehydrogenase; C080001:nifS protein, Bacteria; C051552:persulfides; C006421:1,5-I-AEDANS; C022261:molybdopterin; C440026:ABA3 protein, Arabidopsis; C034278:selenocysteine lyase