PMID:15561708

Citation	Heidenreich, T, Wollers, S, Mendel, RR and Bittner, F (2005) Characterization of the NifS-like domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration. J. Biol. Chem. 280:4213-8
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.
Links	PubMed Online version:10.1074/jbc.M411195200
Keywords	Aldehyde Oxidase/metabolism; Arabidopsis/metabolism; Arabidopsis Proteins; Bacterial Proteins/chemistry; Binding Sites; Catalysis; Coenzymes/chemistry; Cysteine/chemistry; Cytosol/chemistry; Fluorescent Dyes/pharmacology; Genetic Vectors; Iron-Sulfur Proteins/chemistry; Kinetics; Lyases/chemistry; Lysine/chemistry; Metalloproteins/chemistry; Molybdenum/chemistry; Mutagenesis, Site-Directed; Naphthalenesulfonates/pharmacology; Pichia/metabolism; Plant Proteins/chemistry; Protein Binding; Protein Structure, Tertiary; Pteridines/chemistry; Pyridoxal Phosphate/chemistry; Selenocysteine/chemistry; Spectrophotometry; Substrate Specificity; Sulfides/chemistry; Sulfurtransferases/chemistry; Sulfurtransferases/metabolism; Xanthine Dehydrogenase/metabolism
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