Electron Tunneling in Proteins: Coupling Through a β Strand

• DOI: 10.1126/science.7792598
• Publication Date: 2006-10-27T18:19:42Z
• Authors: Ralf Langen; I-Jy Chang; Juris P. Germanas; John H. Richards; Jay R. Winkler; Harry B. Gray
• Keywords: Azurin; Copper protein; Coupling constant

Electron coupling through a β strand has been investigated by measurement of the intramolecular electron-transfer (ET) rates in ruthenium-modified derivatives barrel blue copper protein Pseudomonas aeruginosa azurin. Surface histidines, introduced on methionine-121 mutagenesis, were modified with Ru(2,2′-bipyridine) 2 (imidazole) 2+ complex. The Cu + to Ru 3+ rate constants yielded distance-decay constant 1.1 per angstrom, value close 1.0 angstrom predicted for electron tunneling an idealized strand. Activationless ET combination tunneling-pathway analysis structures azurin and cytochrome c confirm that there is generally efficient network internal (native) redox center surface both proteins.