Chapter 28 Use of ruthenium photoreduction techniques to study electron transfer in cytochrome oxidase.
Ruthenium photoreduction methods are described to study electron transfer from cytochrome c to cytochrome c oxidase and within cytochrome oxidase. Methods are described to prepare a ruthenium cytochrome c derivative Ru-39-Cc, by labeling the single sulfhydryl group on horse K39C with (4-bromomethyl-4'methylbipyridine) (bis-bipyridine)ruthenium(II). The ruthenium complex attached to Cys-39 on the opposite side of the heme crevice does not interfere with the interaction with cytochrome oxidase. Laser flash photolysis of a 1:1 complex between Ru-39-Cc and bovine cytochrome oxidase results in photoreduction of heme c within 1 microsec, followed by electron transfer from heme c to Cu(A) in cytochrome oxidase with a rate constant of 60,000 s(-1) and from Cu(A) to heme a with a rate constant of 20,000 s(-1). A new ruthenium dimer, Ru(2)Z, has been developed to reduce Cu(A) within 1 microsec with a yield of 60%, followed by electron transfer from Cu(A) to heme a and then to the heme a(3)/Cu(B) binuclear center. Methods are described to measure the single-electron reduction of each of the intermediates involved in reduction of oxygen to water by cytochrome oxidase, including P(m), F, O(H), and E.
Department of Chemistry and Biochemistry, University of Arkansas, Fayetteville, Arkansas, USA.
Lois
L
Geren
Bill
B
Durham
Francis
F
Millett
D004579:Electron Transport; D003576:Electron Transport Complex IV / Q000737:chemistry*; D010084:Oxidation-Reduction; D010777:Photochemistry; D012428:Ruthenium / Q000737:chemistry*
D012428:Ruthenium; D003576:Electron Transport Complex IV