| 12525495 |
Xiao K, Engstrom G, Rajagukguk S, Yu CA, Yu L, Durham B, Millett F: Effect of famoxadone on photoinduced electron transfer between the iron-sulfur center and cytochrome c1 in the cytochrome bc1 complex. J Biol Chem. 2003 Mar 28;278(13):11419-26. Epub 2003 Jan 13.
Famoxadone is a new cytochrome bc (1) Q (o) site inhibitor that immobilizes the iron-sulfur protein (ISP) in the b conformation. The effects of famoxadone on electron transfer between the iron-sulfur center (2Fe-2S) and cyt c (1) were studied using a ruthenium dimer to photoinitiate the reaction. The rate constant for electron transfer in the forward direction from 2Fe-2S to cyt c (1) was found to be 16,000 s (-1) in bovine cyt bc (1). Binding famoxadone decreased this rate constant to 1,480 s (-1), consistent with a decrease in mobility of the ISP. Reverse electron transfer from cyt c (1) to 2Fe-2S was found to be biphasic in bovine cyt bc (1) with rate constants of 90,000 and 7,300 s (-1). In the presence of famoxadone, reverse electron transfer was monophasic with a rate constant of 1,420 s (-1). It appears that the rate constants for the release of the oxidized and reduced ISP from the b conformation are the same in the presence of famoxadone. The effects of famoxadone binding on electron transfer were also studied in a series of Rhodobacter sphaeroides cyt bc (1) mutants involving residues at the interface between the Rieske protein and cyt c (1) and/or cyt b. |
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