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Crystal structure of bacterial cytochrome bc1 in complex with azoxystrobin reveals a conformational switch of the Rieske iron–sulfur protein subunit

Journal Article · · Journal of Biological Chemistry
 [1];  [1];  [2];  [1]
  1. National Cancer Institute, Bethesda, MD (United States)
  2. Oklahoma State Univ., Stillwater, OK (United States)
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Cytochrome bc1 complexes (cyt bc1), also known as complex III in mitochondria, are components of the cellular respiratory chain and of the photosynthetic apparatus of non-oxygenic photosynthetic bacteria. They catalyze electron transfer (ET) from ubiquinol to cytochrome c and concomitantly translocate protons across the membrane, contributing to the cross-membrane potential essential for a myriad of cellular activities. This ET-coupled proton translocation reaction requires a gating mechanism that ensures bifurcated electron flow. In this study, we report the observation of the Rieske iron–sulfur protein (ISP) in a mobile state, as revealed by the crystal structure of cyt bc1 from the photosynthetic bacterium Rhodobacter sphaeroides in complex with the fungicide azoxystrobin. Unlike cyt bc1 inhibitors stigmatellin and famoxadone that immobilize the ISP, azoxystrobin causes the ISP-ED to separate from the cyt b subunit and to remain in a mobile state. Analysis of anomalous scattering signals from the iron–sulfur cluster of the ISP suggests the existence of a trajectory for electron delivery. This work supports and solidifies the hypothesis that the bimodal conformation switch of the ISP provides a gating mechanism for bifurcated ET, which is essential to the Q-cycle mechanism of cyt bc1 function.
Research Organization:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Organization:
National Institutes of Health (NIH); USDOE
OSTI ID:
1562697
Journal Information:
Journal of Biological Chemistry, Journal Name: Journal of Biological Chemistry Journal Issue: 32 Vol. 294; ISSN 0021-9258
Publisher:
American Society for Biochemistry and Molecular BiologyCopyright Statement
Country of Publication:
United States
Language:
ENGLISH

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
59 BASIC BIOLOGICAL SCIENCES
conformation switch
conformational change
cytochrome
cytochrome bc1
electron transfer
electron transfer mechanism
respiratory chain
respiratory inhibitors
x-ray crystallography