Characterization and redox properties of cytochrome c552 from Thermus thermophilus adsorbed on different self‐assembled thiol monolayers, used to model the chemical environment of the redox partner

Abstract The structure of cytochrome c 552 (Cyt‐ c 552 ) from Thermus thermophilus shows many differences to other c‐ type cytochromes. The rich lysine domain close to the heme does not exist in this cytochrome, allowing us to postulate that the interaction with its redox partner must be different to the cytochrome c /cytochrome c oxidase interaction. We report a study of Cyt‐ c 552 adsorbed on self‐assembled monolayers (SAMs) of functionalized alkanethiols used to mimic the chemical properties of its redox partner ( ba 3 ‐oxydase). Hydrophilic (—COOH), polar (—OH), hydrophobic (—CH 3 ), and mixed (—OH/—CH 3 ) SAMs grafted on roughened silver electrodes were characterized by X‐ray photoelectron spectroscopy. Surface enhanced resonance Raman spectroscopy (SERRS) was employed to determine the structure and the redox properties ( E ° and number of transferred electron) of the heme of Cyt‐ c 552 adsorbed on roughened silver electrodes coated by the different SAMs. The surface that most closely models the environment of the ba 3 ‐oxidase is a mixed SAM formed by 50% polar [Ag–(CH 2 ) 5 –CH 2 OH] and 50% hydrophobic [Ag–(CH 2 ) 5 –CH 3 ] alkanethiols. Only the native form B1(6cLS) of Cyt‐ c 552 is detected by SERRS when the protein is adsorbed on such a surface that promotes a protein orientation favorable for the electron transfer (number of transferred electron = 1). We shall discuss the differences and similarities of the electron‐transfer mechanism of Cyt‐ c 552 compared to cyt‐ c . © 2005 Wiley Periodicals, Inc. Biopolymers 81: 407–418, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com