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Papers In Press, published online ahead of print November 22, 2004
Department of Botany, Technical University of Braunschweig, Braunschweig D-38106
Corresponding Author: r.mendel{at}tu-bs.de
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 N-terminal domain sharing significant similarities to NifS proteins which 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 a 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 that both are proposed to be involved in ironsulfur cluster formation ABA3 is proposed to be a third and cytosolic NifS-like cysteine desulfurase in A. thaliana. However, its sulfur transferase activity is used for posttranslational activation of molybdenum enzymes rather than for iron-sulfur cluster assembly.
J. Biol. Chem, 10.1074/jbc.M411195200
Submitted on September 30, 2004
Revised on November 10, 2004
Accepted on November 22, 2004
Characterization of the NifS-like domain of ABA3 from arabidopsis thaliana provides insight into the mechanism of molybdenum cofactor sulfuration
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