Aromatic residues may enhance intramolecular electron transfer in azurin

The relevant electron transfer (ET) routes from electron donor to acceptor at the transition state were identified using the structure-dependent pathway model. The three-dimensional structures of Pseudomonas aeruginosa azurin and of its mutants were used for pathway calculations for the intramolecular ET. Two major ET routes in all of the azurins were predicted from the calculations. These are one longer path through the peptide chain to the copper-ligating imidazole of His46 and one shorter path through the buried residue 48, which requires a leap from Val31 to this side chain and then to the copper ligand, Cys 112. Aromatic residues have been found to be so positioned to probably enhance the electronic coupling.