Domain conformational switch of the iron-sulfur protein in cytochrome bc1 complex is induced by the electron transfer from cytochrome bL to bH.
Intensive biochemical, biophysical and structural studies of the cytochrome (cyt) bc(1) complex in the past have led to the formulation of the "protonmotive Q-cycle" mechanism for electron and proton transfer in this vitally important complex. The key step of this mechanism is the separation of electrons during the oxidation of a substrate quinol at the Q(P) site with both electrons transferred simultaneously to ISP and cyt b(L) when the extrinsic domain of ISP (ISP-ED) is located at the b-position. Pre-steady state fast kinetic analysis of bc(1) demonstrates that the reduced ISP-ED moves to the c(1)-position to reduce cyt c(1) only after the reduced cyt b(L) is oxidized by cyt b(H). However, the question of how the conformational switch of ISP-ED is initiated remains unanswered. The results obtained from analysis of inhibitory efficacy and binding affinity of two types of Q(P) site inhibitors, Pm and Pf, under various redox states of the bc(1) complex, suggest that the electron transfer from heme b(L) to b(H) is the driving force for the releasing of the reduced ISP-ED from the b-position to c(1)-position to reduce cyt c(1).
Yu
Chang-An
CA
Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA. cayuq@okstate.edu
Cen
Xiaowei
X
Ma
He-Wen
HW
Yin
Ying
Y
Yu
Linda
L
Esser
Lothar
L
Xia
Di
D
D000818:Animals; D001665:Binding Sites; D002417:Cattle; D002645:Chickens; D045303:Cytochromes b / Q000378:metabolism*; D004579:Electron Transport; D014450:Electron Transport Complex III / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism*; D008958:Models, Molecular; D011487:Protein Conformation; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism
D007506:Iron-Sulfur Proteins; D029701:Saccharomyces cerevisiae Proteins; D045303:Cytochromes b; D014450:Electron Transport Complex III