title: Electron tunneling in proteins: coupling through a beta strand.
abstract: Electron coupling through a beta strand has been investigated by measurement of the intramolecular electron-transfer (ET) rates in ruthenium-modified derivatives of the beta barrel blue copper protein Pseudomonas aeruginosa azurin. Surface histidines, introduced on the methionine-121 beta strand by mutagenesis, were modified with a Ru(2,2'-bipyridine)2(imidazole)2+ complex. The Cu+ to Ru3+ rate constants yielded a distance-decay constant of 1.1 per angstrom, a value close to the distance-decay constant of 1.0 per angstrom predicted for electron tunneling through an idealized beta strand. Activationless ET rate constants in combination with a tunneling-pathway analysis of the structures of azurin and cytochrome c confirm that there is a generally efficient network for coupling the internal (native) redox center to the surface of both proteins.
authors.affiliation: Beckman Institute, California Institute of Technology, Pasadena 91125, USA.
authors.forename: R
authors.initials: R
authors.lastname: Langen
authors.forename: I J
authors.initials: IJ
authors.lastname: Chang
authors.forename: J P
authors.initials: JP
authors.lastname: Germanas
authors.forename: J H
authors.initials: JH
authors.lastname: Richards
authors.forename: J R
authors.initials: JR
authors.lastname: Winkler
authors.forename: H B
authors.initials: HB
authors.lastname: Gray
mesh_terms: D001400:Azurin / Q000737:chemistry* / Q000378:metabolism; D001665:Binding Sites; D003574:Cytochrome c Group / Q000737:chemistry* / Q000378:metabolism; D004579:Electron Transport; D008956:Models, Chemical; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D011550:Pseudomonas aeruginosa; D012428:Ruthenium / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D003574:Cytochrome c Group; D001400:Azurin; D012428:Ruthenium