In vivo iron-sulfur cluster formation
Estella C Raulfs1, Ina P O'Carroll, Patricia C Dos Santos
1Department of Biochemistry, Virginia Tech, Blacksburg, VA 24061, USA.
Summary
Iron-sulfur cluster assembly in bacteria involves the scaffold protein IscU. Overproduction reveals key intermediate forms, validating the scaffold hypothesis for iron-sulfur protein maturation.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- Iron-sulfur (Fe-S) clusters are essential cofactors for numerous proteins.
- The scaffold protein IscU is proposed to be central to Fe-S cluster biogenesis.
- Understanding Fe-S cluster assembly is crucial for various biological processes.
Purpose of the Study:
- To investigate the in vivo stages of iron-sulfur cluster assembly mediated by IscU.
- To validate the scaffold hypothesis for Fe-S cluster biogenesis.
- To elucidate the dynamic interactions between IscU and other proteins in the assembly pathway.
Main Methods:
- Overproduction of the Azotobacter vinelandii [Fe-S] cluster biosynthetic machinery.
- Analysis of IscU species under conditions of excess machinery production.
- Site-directed mutagenesis of IscU (Asp39 to Ala) to trap intermediates.
Main Results:
- Overproduction led to the accumulation of apo-IscU, [2Fe-2S] cluster-loaded IscU, and IscU-IscS complexes.
- A mutant IscU (D39A) trapped a stable, oxygen-resistant [Fe-S] species within an IscU-IscS complex.
- These findings suggest distinct, dynamic stages in Fe-S cluster assembly.
Conclusions:
- The results strongly support the scaffold hypothesis for Fe-S cluster assembly.
- In vivo Fe-S cluster formation is a dynamic process involving reversible IscU-IscS interactions.
- The study provides insights into the mechanism of iron-sulfur protein maturation.
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