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Zhan J, Zeher A, Huang R, Tang WK, Jenkins LM, Xia D. Conformations of Bcs1L undergoing ATP hydrolysis suggest a concerted translocation mechanism for folded iron-sulfur protein substrate. Nat Commun 2024; 15:4655. [PMID: 38821922 PMCID: PMC11143374 DOI: 10.1038/s41467-024-49029-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Accepted: 05/20/2024] [Indexed: 06/02/2024] Open
Abstract
The human AAA-ATPase Bcs1L translocates the fully assembled Rieske iron-sulfur protein (ISP) precursor across the mitochondrial inner membrane, enabling respiratory Complex III assembly. Exactly how the folded substrate is bound to and released from Bcs1L has been unclear, and there has been ongoing debate as to whether subunits of Bcs1L act in sequence or in unison hydrolyzing ATP when moving the protein cargo. Here, we captured Bcs1L conformations by cryo-EM during active ATP hydrolysis in the presence or absence of ISP substrate. In contrast to the threading mechanism widely employed by AAA proteins in substrate translocation, subunits of Bcs1L alternate uniformly between ATP and ADP conformations without detectable intermediates that have different, co-existing nucleotide states, indicating that the subunits act in concert. We further show that the ISP can be trapped by Bcs1 when its subunits are all in the ADP-bound state, which we propose to be released in the apo form.
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Affiliation(s)
- Jingyu Zhan
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Allison Zeher
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- NIH Intramural Cryo-EM Consortium (NICE), Bethesda, MD, USA
| | - Rick Huang
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
- NIH Intramural Cryo-EM Consortium (NICE), Bethesda, MD, USA
| | - Wai Kwan Tang
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Lisa M Jenkins
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, 20892, USA.
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2
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Esser L, Zhou F, Zeher A, Wu W, Huang R, Yu CA, Lane KD, Wellems TE, Xia D. Structure of complex III with bound antimalarial agent CK-2-68 provides insights into selective inhibition of Plasmodium cytochrome bc 1 complexes. J Biol Chem 2023; 299:104860. [PMID: 37236355 PMCID: PMC10404626 DOI: 10.1016/j.jbc.2023.104860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Revised: 05/17/2023] [Accepted: 05/18/2023] [Indexed: 05/28/2023] Open
Abstract
Among the various components of the protozoan Plasmodium mitochondrial respiratory chain, only Complex III is a validated cellular target for antimalarial drugs. The compound CK-2-68 was developed to specifically target the alternate NADH dehydrogenase of the malaria parasite respiratory chain, but the true target for its antimalarial activity has been controversial. Here, we report the cryo-EM structure of mammalian mitochondrial Complex III bound with CK-2-68 and examine the structure-function relationships of the inhibitor's selective action on Plasmodium. We show that CK-2-68 binds specifically to the quinol oxidation site of Complex III, arresting the motion of the iron-sulfur protein subunit, which suggests an inhibition mechanism similar to that of Pf-type Complex III inhibitors such as atovaquone, stigmatellin, and UHDBT. Our results shed light on the mechanisms of observed resistance conferred by mutations, elucidate the molecular basis of the wide therapeutic window of CK-2-68 for selective action of Plasmodium vs. host cytochrome bc1, and provide guidance for future development of antimalarials targeting Complex III.
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Affiliation(s)
- Lothar Esser
- Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA
| | - Fei Zhou
- Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA
| | - Allison Zeher
- Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA; NIH Intramural Cryo-EM Consortium (NICE), Bethesda, Maryland, USA
| | - Weimin Wu
- Center for Molecular Microscopy, Center for Cancer Research, National Cancer Institute, NIH, Frederick, Maryland, USA
| | - Rick Huang
- Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA; NIH Intramural Cryo-EM Consortium (NICE), Bethesda, Maryland, USA
| | - Chang-An Yu
- Department of Biochemistry, Oklahoma State University, Stillwater, Oklahoma, USA
| | - Kristin D Lane
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
| | - Thomas E Wellems
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, NIH, Bethesda, Maryland, USA
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research National Cancer Institute, NIH, Bethesda, Maryland, USA.
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3
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Esser L, Zhou F, Yu CA, Xia D. Crystal structure of bacterial cytochrome bc 1 in complex with azoxystrobin reveals a conformational switch of the Rieske iron-sulfur protein subunit. J Biol Chem 2019; 294:12007-12019. [PMID: 31182483 DOI: 10.1074/jbc.ra119.008381] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Revised: 06/06/2019] [Indexed: 11/06/2022] Open
Abstract
Cytochrome bc 1 complexes (cyt bc 1), 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. Here, we report the observation of the Rieske iron-sulfur protein (ISP) in a mobile state, as revealed by the crystal structure of cyt bc 1 from the photosynthetic bacterium Rhodobacter sphaeroides in complex with the fungicide azoxystrobin. Unlike cyt bc 1 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 bc 1 function.
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Affiliation(s)
- Lothar Esser
- Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Fei Zhou
- Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892
| | - Chang-An Yu
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892.
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4
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Mechanisms of Superoxide Generation and Signaling in Cytochrome bc Complexes. ADVANCES IN PHOTOSYNTHESIS AND RESPIRATION 2016. [DOI: 10.1007/978-94-017-7481-9_20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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5
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Hasan SS, Proctor EA, Yamashita E, Dokholyan NV, Cramer WA. Traffic within the cytochrome b6f lipoprotein complex: gating of the quinone portal. Biophys J 2015; 107:1620-8. [PMID: 25296314 DOI: 10.1016/j.bpj.2014.08.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Revised: 07/29/2014] [Accepted: 08/05/2014] [Indexed: 12/24/2022] Open
Abstract
The cytochrome bc complexes b6f and bc1 catalyze proton-coupled quinol/quinone redox reactions to generate a transmembrane proton electrochemical gradient. Quinol oxidation on the electrochemically positive (p) interface of the complex occurs at the end of a narrow quinol/quinone entry/exit Qp portal, 11 Å long in bc complexes. Superoxide, which has multiple signaling functions, is a by-product of the p-side quinol oxidation. Although the transmembrane core and the chemistry of quinone redox reactions are conserved in bc complexes, the rate of superoxide generation is an order of magnitude greater in the b6f complex, implying that functionally significant differences in structure exist between the b6f and bc1 complexes on the p-side. A unique structure feature of the b6f p-side quinol oxidation site is the presence of a single chlorophyll-a molecule whose function is unrelated to light harvesting. This study describes a cocrystal structure of the cytochrome b6f complex with the quinol analog stigmatellin, which partitions in the Qp portal of the bc1 complex, but not effectively in b6f. It is inferred that the Qp portal is partially occluded in the b6f complex relative to bc1. Based on a discrete molecular-dynamics analysis, occlusion of the Qp portal is attributed to the presence of the chlorophyll phytyl tail, which increases the quinone residence time within the Qp portal and is inferred to be a cause of enhanced superoxide production. This study attributes a novel (to our knowledge), structure-linked function to the otherwise enigmatic chlorophyll-a in the b6f complex, which may also be relevant to intracellular redox signaling.
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Affiliation(s)
- S Saif Hasan
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, Indiana
| | - Elizabeth A Proctor
- Curriculum in Bioinformatics and Computational Biology, University of North Carolina, Chapel Hill, North Carolina
| | - Eiki Yamashita
- Osaka University, Institute for Protein Research, Suita, Osaka, Japan
| | - Nikolay V Dokholyan
- Department of Biochemistry and Biophysics, University of North Carolina, Chapel Hill, North Carolina
| | - William A Cramer
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University, West Lafayette, Indiana.
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6
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Xiao YM, Esser L, Zhou F, Li C, Zhou YH, Yu CA, Qin ZH, Xia D. Studies on inhibition of respiratory cytochrome bc1 complex by the fungicide pyrimorph suggest a novel inhibitory mechanism. PLoS One 2014; 9:e93765. [PMID: 24699450 PMCID: PMC3974799 DOI: 10.1371/journal.pone.0093765] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 03/05/2014] [Indexed: 11/29/2022] Open
Abstract
The respiratory chain cytochrome bc1 complex (cyt bc1) is a major target of numerous antibiotics and fungicides. All cyt bc1 inhibitors act on either the ubiquinol oxidation (QP) or ubiquinone reduction (QN) site. The primary cause of resistance to bc1 inhibitors is target site mutations, creating a need for novel agents that act on alternative sites within the cyt bc1 to overcome resistance. Pyrimorph, a synthetic fungicide, inhibits the growth of a broad range of plant pathogenic fungi, though little is known concerning its mechanism of action. In this study, using isolated mitochondria from pathogenic fungus Phytophthora capsici, we show that pyrimorph blocks mitochondrial electron transport by affecting the function of cyt bc1. Indeed, pyrimorph inhibits the activities of both purified 11-subunit mitochondrial and 4-subunit bacterial bc1 with IC50 values of 85.0 μM and 69.2 μM, respectively, indicating that it targets the essential subunits of cyt bc1 complexes. Using an array of biochemical and spectral methods, we show that pyrimorph acts on an area near the QP site and falls into the category of a mixed-type, noncompetitive inhibitor with respect to the substrate ubiquinol. In silico molecular docking of pyrimorph to cyt b from mammalian and bacterial sources also suggests that pyrimorph binds in the vicinity of the quinol oxidation site.
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Affiliation(s)
- Yu-Mei Xiao
- Department of Applied Chemistry, China Agricultural University, Beijing, China
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, United States of America
| | - Lothar Esser
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, United States of America
| | - Fei Zhou
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, United States of America
| | - Chang Li
- Department of Applied Chemistry, China Agricultural University, Beijing, China
| | - Yi-Hui Zhou
- Department of Applied Chemistry, China Agricultural University, Beijing, China
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, United States of America
| | - Chang-An Yu
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma, United States of America
| | - Zhao-Hai Qin
- Department of Applied Chemistry, China Agricultural University, Beijing, China
- * E-mail: (ZQ); (DX)
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland, United States of America
- * E-mail: (ZQ); (DX)
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7
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Baniulis D, Hasan SS, Stofleth JT, Cramer WA. Mechanism of enhanced superoxide production in the cytochrome b(6)f complex of oxygenic photosynthesis. Biochemistry 2013; 52:8975-83. [PMID: 24298890 DOI: 10.1021/bi4013534] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The specific rate of superoxide (O2(•-)) production in the purified active crystallizable cytochrome b6f complex, normalized to the rate of electron transport, has been found to be more than an order of magnitude greater than that measured in isolated yeast respiratory bc1 complex. The biochemical and structural basis for the enhanced production of O2(•-) in the cytochrome b6f complex compared to that in the bc1 complex is discussed. The higher rate of superoxide production in the b6f complex could be a consequence of an increased residence time of plastosemiquinone/plastoquinol in its binding niche near the Rieske protein iron-sulfur cluster, resulting from (i) occlusion of the quinone portal by the phytyl chain of the unique bound chlorophyll, (ii) an altered environment of the proton-accepting glutamate believed to be a proton acceptor from semiquinone, or (iii) a more negative redox potential of the heme bp on the electrochemically positive side of the complex. The enhanced rate of superoxide production in the b6f complex is physiologically significant as the chloroplast-generated reactive oxygen species (ROS) functions in the regulation of excess excitation energy, is a source of oxidative damage inflicted during photosynthetic reactions, and is a major source of ROS in plant cells. Altered levels of ROS production are believed to convey redox signaling from the organelle to the cytosol and nucleus.
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Affiliation(s)
- Danas Baniulis
- Department of Biological Sciences, Hockmeyer Hall of Structural Biology, Purdue University , West Lafayette, Indiana 47907, United States
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8
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Zhou F, Yin Y, Su T, Yu L, Yu CA. Oxygen dependent electron transfer in the cytochrome bc(1) complex. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:2103-9. [PMID: 22922016 DOI: 10.1016/j.bbabio.2012.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Revised: 07/16/2012] [Accepted: 08/13/2012] [Indexed: 10/28/2022]
Abstract
The effect of molecular oxygen on the electron transfer activity of the cytochrome bc(1) complex was investigated by determining the activity of the complex under the aerobic and anaerobic conditions. Molecular oxygen increases the activity of Rhodobacter sphaeroides bc(1) complex up to 82%, depending on the intactness of the complex. Since oxygen enhances the reduction rate of heme b(L), but shows no effect on the reduction rate of heme b(H), the effect of oxygen in the electron transfer sequence of the cytochrome bc(1) complex is at the step of heme b(L) reduction during bifurcated oxidation of ubiquinol.
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Affiliation(s)
- Fei Zhou
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA
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9
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Yin Y, Yang S, Yu L, Yu CA. Reaction mechanism of superoxide generation during ubiquinol oxidation by the cytochrome bc1 complex. J Biol Chem 2010; 285:17038-45. [PMID: 20371599 DOI: 10.1074/jbc.m110.104364] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In addition to its main functions of electron transfer and proton translocation, the cytochrome bc(1) complex (bc(1)) also catalyzes superoxide anion (O(2)(*)) generation upon oxidation of ubiquinol in the presence of molecular oxygen. The reaction mechanism of superoxide generation by bc(1) remains elusive. The maximum O(2)(*) generation activity is observed when the complex is inhibited by antimycin A or inactivated by heat treatment or proteinase K digestion. The fact that the cytochrome bc(1) complex with less structural integrity has higher O(2)(*)-generating activity encouraged us to speculate that O(2)(*) is generated inside the complex, perhaps in the hydrophobic environment of the Q(P) pocket through bifurcated oxidation of ubiquinol by transferring its two electrons to a high potential electron acceptor, iron-sulfur cluster, and a low potential heme b(L) or molecular oxygen. If this speculation is correct, then one should see more O(2)(*) generation upon oxidation of ubiquinol by a high potential oxidant, such as cytochrome c or ferricyanide, in the presence of phospholipid vesicles or detergent micelles than in the hydrophilic conditions, and this is indeed the case. The protein subunits, at least those surrounding the Q(P) pocket, may play a role either in preventing the release of O(2)(*) from its production site to aqueous environments or in preventing O(2) from getting access to the hydrophobic Q(P) pocket and might not directly participate in superoxide production.
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Affiliation(s)
- Ying Yin
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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Wang Q, Yu L, Yu CA. Cross-talk between mitochondrial malate dehydrogenase and the cytochrome bc1 complex. J Biol Chem 2010; 285:10408-14. [PMID: 20075069 DOI: 10.1074/jbc.m109.085787] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The interactions between the mitochondrial cytochrome bc(1) complex and matrix-soluble proteins were studied by a precipitation pulldown technique. Purified, detergent-dispersed bc(1) complex was incubated with mitochondrial matrix proteins followed by dialysis in the absence of detergent. The interacting protein(s) was co-precipitated with bc(1) complex upon centrifugation. One of the matrix proteins pulled down by bc(1) complex was identified as mitochondrial malate dehydrogenase (MDH) by matrix-assisted laser desorption ionization time-of-flight mass spectrometry and confirmed by Western blotting with anti-MDH antibody. Using a cross-linking technique, subunits I, II (core I and II), and V of the bc(1) complex were identified as the interacting sites for MDH. Incubating purified MDH with the detergent dispersed bc(1) complex results in an increase of the activities of both the bc(1) complex and MDH. The effect of the bc(1) complex on the activities of MDH is unidirectional (oxaloacetate --> malate). These results suggest that the novel cross-talk between citric acid cycle enzymes and electron transfer chain complexes might play a regulatory role in mitochondrial bioenergetics.
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Affiliation(s)
- Qiyu Wang
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078, USA
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