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Electron transfer in ferredoxin: are tunneling pathways evolutionarily conserved?
Iraj Daizadeh1, Dmitry M Medvedev, Alexei A Stuchebrukhov
1Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA, USA.
Molecular Biology and Evolution
|March 29, 2002
Summary
This study identifies conserved electron transfer pathways in ferredoxins, primarily through cysteine ligands, explaining why mutations elsewhere have minimal impact on transfer rates.
Area of Science:
- Biochemistry
- Biophysics
- Computational Biology
Background:
- Ferredoxins are crucial electron transfer proteins.
- Understanding electron transfer pathways is key to protein function.
- Clostridium acidurici ferredoxin provides a model system for studying these pathways.
Purpose of the Study:
- To theoretically investigate electron transfer pathways in Clostridium acidurici ferredoxin.
- To identify the key amino acid residues and pathways involved in electron tunneling.
- To explore the evolutionary conservation of these pathways.
Main Methods:
- Semiempirical extended Hückel level for electronic structure.
- Quantum mechanical tunneling currents for pathway calculation.
- In silico mutation analysis of amino acid residues.
Main Results:
- Two primary electron transfer pathways identified: a strong direct pathway (Cys14-Cys43) and a weaker indirect pathway (Cys14-Ile23-Cys18).
- Cysteine ligands are the main conductors of electron current.
- Ile23 mutation showed no significant change in electron transfer rate.
- Sequence analysis revealed Ile23 is highly variable, unlike conserved cysteines.
Conclusions:
- Electron tunneling pathways in ferredoxins are evolutionarily conserved.
- Conserved cysteine residues form the primary electron transfer conduit.
- Mutations in non-essential amino acids do not significantly alter electron transfer rates.