Complete Electron Tunneling Pathways from FMN to N2 of Respiratory Complex I

Specific peptide residues serve as electronic wires connecting neighboring Fe/S clusters.

Individual electron tunneling paths involve up to three protein residues, including two cysteine ligands and one additional key residue.

The clusters in the protein are oriented in a specific way - corner to corner - with Cys ligands mostly pointing toward each other, which is clearly the most efficient way to transfer electrons from one cluster to another.