Mitochondrial cysteine desulfurase

Project Details


Cysteine desulfurases perform essential functions in releasing sulfur from cysteine, forming a
covalent persulfide, and channeling the persulfide sulfur to biologically critical recipients e.g.
ironsulfur (Fe-S) clusters and thiolated tRNAs. The activity of cysteine desulfurase cannot be
replaced by exogenously supplied sulfide or by other sulfur metabolizing enzymes, and thus
cysteine desulfurase is essential for cell viability. The eukaryotic cysteine desulfurase is encoded
by a single nuclear gene and is found primarily in mitochondria. In Saccharomyces cerevisiae
mitochondria, the cysteine desulfurase protein Nfs1 is assembled in a large protein complex with
a recently identified special accessory protein called Isd11. We found that Isd11 is required for
Nfs1 cysteine desulfurase activity. Thus, Nfs1 and Isd11 expressed together in bacteria are
assembled into an active complex, while these components expressed separately are inactive.
Here we propose to characterize the active Nfs1/Isd11 complex, and regulation of its cysteine
desulfurase activity by Fe-S cluster scaffold proteins, Isu. Aim 1 is to determine the role of yeast
Isd11 in the active Nfs1/Isd11 cysteine desulfurase complex. Experiments will be performed using
bacterial expressed and purified proteins, and also in a more physiological context using isolated
intact mitochondria. Aim 2 is to characterize formation of persulfide sulfur on Nfs1/Isd11 in
isolated intact mitochondria, with focus on the regulatory effect of the D37A mutation of Isu.
The significance derives from the essential role of cysteine desulfurase for viability of all human
cells. The enzyme is found primarily in mitochondria and is required for Fe-S cluster synthesis
and tRNA thiolation in mitochondria, both are essential processes. The identification of specific
diseases arising from defective Fe-S cluster assembly (e.g. Friedreich's ataxia, sideroblastic
anemia, and mitochondrial myopathy) represents the tip of the iceberg. The recent discovery of a
key role of Fe-S clusters in DNA repair and genome stability suggests that cysteine desulfurases
are involved in these processes.
Effective start/end date9/30/098/31/12


  • National Institutes of Health: $331,138.00
  • National Institutes of Health: $331,645.00


  • Medicine(all)
  • Biochemistry, Genetics and Molecular Biology(all)

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