A novel eukaryotic factor for cytosolic Fe-S cluster assembly.

Area of Science:

• Biochemistry
• Molecular Biology
• Yeast Genetics

Background:

• Iron regulatory protein 1 (IRP1) interconverts between its iron-sensing form and cytosolic aconitase via [4Fe-4S] cluster assembly/disassembly.
• Understanding the mechanisms of cytosolic iron-sulfur cluster biogenesis is crucial for cellular iron homeostasis.

Purpose of the Study:

• To identify genes essential for the conversion of IRP1 to cytosolic aconitase in Saccharomyces cerevisiae.
• To characterize a novel gene involved in cytosolic iron-sulfur cluster assembly.

Main Methods:

• Genetic screening in yeast to isolate mutants defective in IRP1 conversion.
• Biochemical assays to measure enzyme activity (c-aconitase, Leu1p).
• Electron paramagnetic resonance (EPR) spectroscopy to detect Fe-S clusters.
• Subcellular localization studies of the identified protein.

Main Results:

• Identification of a novel essential gene, CFD1, required for IRP1 to c-aconitase conversion.
• CFD1 encodes a putative P-loop ATPase, Cfd1p, localized to the cytoplasm.
• Mutations in CFD1 severely impaired cytosolic Fe-S protein activity (c-aconitase, Leu1p) but not mitochondrial Fe-S proteins.
• CFD1 mutants showed a lack of detectable Fe-S clusters in c-aconitase, indicating a defect in cluster assembly.

Conclusions:

• Cfd1p is the first described eukaryotic cytoplasmic factor essential for Fe-S cluster assembly.
• CFD1 plays a critical role in the biogenesis of cytosolic iron-sulfur proteins.
• This discovery provides new insights into cellular iron metabolism and Fe-S cluster pathways.