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Publication Abstract from PubMed

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 nonoxygeneic 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. Here, 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 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 Qcycle mechanism of cyt bc1 function.

The Crystal Structure of Bacterial Cytochrome bc1 in Complex with Azoxystrobin Reveals a Conformation Switch of the Rieske Iron-Sulfur Protein Subunit.,Esser L, Zhou F, Yu CA, Xia D J Biol Chem. 2019 Jun 10. pii: RA119.008381. doi: 10.1074/jbc.RA119.008381. PMID:31182483^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.