Characterization of the NifS-like domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration.

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Heidenreich T, Wollers S, Mendel RR, Bittner F

Characterization of the NifS-like domain of ABA3 from Arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration.

J Biol Chem. 2005 Feb 11;280(6):4213-8. Epub 2004 Nov 22.

PubMed ID

15561708 [ View in PubMed

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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.

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Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Pyridoxal phosphate	Molybdenum cofactor sulfurase	Protein	Humans	Unknown	Cofactor	Details