Understanding the Mechanism of Short-Range Electron Transfer Using an Immobilized Cupredoxin

• Published in: Journal of the American Chemical Society Vol. 134; no. 29; pp. 11848 - 11851
• Main Authors: Monari, Stefano, Battistuzzi, Gianantonio, Bortolotti, Carlo A, Yanagisawa, Sachiko, Sato, Katsuko, Li, Chan, Salard, Isabelle, Kostrz, Dorota, Borsari, Marco, Ranieri, Antonio, Dennison, Christopher, Sola, Marco
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 25.07.2012
• Subjects: Azurin - chemistry; Azurin - genetics; Azurin - metabolism; Binding Sites; Biosensing Techniques; Chemical Sciences; Copper - metabolism; Electron Transport; Immobilized Proteins - chemistry; Immobilized Proteins - genetics; Immobilized Proteins - metabolism; Life Sciences; Models, Molecular; Mutation; Pseudomonas aeruginosa - chemistry; Pseudomonas aeruginosa - enzymology; Pseudomonas aeruginosa - genetics; Pseudomonas aeruginosa - metabolism; Thermodynamics
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja303425b

The hydrophobic patch of azurin (AZ) from Pseudomonas aeruginosa is an important recognition surface for electron transfer (ET) reactions. The influence of changing the size of this region, by mutating the C-terminal copper-binding loop, on the ET reactivity of AZ adsorbed on gold electrodes modified with alkanethiol self-assembled monolayers (SAMs) has been studied. The distance-dependence of ET kinetics measured by cyclic voltammetry using SAMs of variable chain length, demonstrates that the activation barrier for short-range ET is dominated by the dynamics of molecular rearrangements accompanying ET at the AZ-SAM interface. These include internal electric field-dependent low-amplitude protein motions and the reorganization of interfacial water molecules, but not protein reorientation. Interfacial molecular dynamics also control the kinetics of short-range ET for electrostatically and covalently immobilized cytochrome c. This mechanism therefore may be utilized for short-distance ET irrespective of the type of metal center, the surface electrostatic potential, and the nature of the protein–SAM interaction.