scholarly journals Cryo-EM Structures of Respiratory bc1-cbb3 type CIII2CIV Supercomplex and Electronic Communication Between the Complexes

2020 ◽  
Author(s):  
Stefan Steimle ◽  
Trevor VanEeuwen ◽  
Yavuz Ozturk ◽  
Hee Jong Kim ◽  
Merav Braitbard ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Rhodobacter Capsulatus ◽  
Structural Features ◽  
Complex Iii ◽  
Transport Pathways ◽  
Gram Negative ◽  
Atp Production ◽  
Growth Modes ◽  
Respiratory Electron Transport

AbstractThe respiratory electron transport complexes convey electrons from nutrients to oxygen and generate a proton-motive force used for energy (ATP) production in cells. These enzymes are conserved among organisms, and organized as individual complexes or combined forming large super-complexes (SC). Bacterial electron transport pathways are more branched than those of mitochondria and contain multiple variants of such complexes depending on their growth modes. The Gram-negative species deploy a mitochondrial-like cytochrome bc1 (Complex III, CIII2), and may have bacteria-specific cbb3-type cytochrome c oxidases (Complex IV, CIV) in addition to, or instead of, the canonical aa3-type CIV. Electron transfer between these complexes is mediated by two different carriers: the soluble cytochrome c2 which is similar to mitochondrial cytochrome c and the membrane-anchored cytochrome cy which is unique to bacteria. Here, we report the first cryo-EM structure of a respiratory bc1-cbb3 type SC (CIII2CIV, 5.2Å resolution) and several conformers of native CIII2 (3.3Å resolution) from the Gram-negative bacterium Rhodobacter capsulatus. The SC contains all catalytic subunits and cofactors of CIII2 and CIV, as well as two extra transmembrane helices attributed to cytochrome cy and the assembly factor CcoH. Remarkably, some of the native CIII2 are structural heterodimers with different conformations of their [2Fe-2S] cluster-bearing domains. The unresolved cytochrome c domain of cy suggests that it is mobile, and it interacts with CIII2CIV differently than cytochrome c2. Distance requirements for electron transfer suggest that cytochrome cy and cytochrome c2 donate electrons to heme cp1 and heme cp2 of CIV, respectively. For the first time, the CIII2CIV architecture and its electronic connections establish the structural features of two separate respiratory electron transport pathways (membrane-confined and membrane-external) between its partners in Gram-negative bacteria.

scholarly journals Cryo-EM structures of engineered active bc1-cbb3 type CIII2CIV super-complexes and electronic communication between the complexes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Stefan Steimle ◽  
Trevor van Eeuwen ◽  
Yavuz Ozturk ◽  
Hee Jong Kim ◽  
Merav Braitbard ◽  
...  
Keyword(s):  
Electron Transport ◽  
Complex Iii ◽  
Gram Negative Bacteria ◽  
Transport Pathways ◽  
Gram Negative ◽  
Assembly Factor ◽  
Electron Transport Complexes ◽  
Respiratory Electron Transport

AbstractRespiratory electron transport complexes are organized as individual entities or combined as large supercomplexes (SC). Gram-negative bacteria deploy a mitochondrial-like cytochrome (cyt) bc1 (Complex III, CIII2), and may have specific cbb3-type cyt c oxidases (Complex IV, CIV) instead of the canonical aa3-type CIV. Electron transfer between these complexes is mediated by soluble (c2) and membrane-anchored (cy) cyts. Here, we report the structure of an engineered bc1-cbb3 type SC (CIII2CIV, 5.2 Å resolution) and three conformers of native CIII2 (3.3 Å resolution). The SC is active in vivo and in vitro, contains all catalytic subunits and cofactors, and two extra transmembrane helices attributed to cyt cy and the assembly factor CcoH. The cyt cy is integral to SC, its cyt domain is mobile and it conveys electrons to CIV differently than cyt c2. The successful production of a native-like functional SC and determination of its structure illustrate the characteristics of membrane-confined and membrane-external respiratory electron transport pathways in Gram-negative bacteria.

scholarly journals Cryo-EM Structures of Respiratory bc1-cbb3 type CIII2CIV Supercomplex and Electronic Communication Between the Complexes

2020 ◽  
Author(s):  
Stefan Steimle ◽  
Trevor Van Eeuwen ◽  
Yavuz Ozturk ◽  
Hee Jong Kim ◽  
Merav Braitbard ◽  
...  
Keyword(s):  
Electron Transport ◽  
Structural Characteristics ◽  
Complex Iii ◽  
Gram Negative Bacteria ◽  
Transport Pathways ◽  
Gram Negative ◽  
Assembly Factor ◽  
Cyt C ◽  
Functional Relevance ◽  
Electron Transport Complexes

Abstract Respiratory electron transport complexes are organized as individual entities or combined as large super-complexes (SC). The Gram-negative bacteria deploy a mitochondrial-like cytochrome (cyt) bc1 (Complex III, CIII2), and may have specific cbb3-type cyt c oxidases (Complex IV, CIV) instead of the canonical aa3-type CIV. Electron transfer between these complexes is mediated by soluble (c2) and membrane-anchored (cy) cyts. Here, we report the first structure of a bc1-cbb3 type SC (CIII2CIV, 5.2Å resolution) and three conformers of native CIII2 (3.3Å resolution) of functional relevance. The SC contains all catalytic subunits and cofactors as well as two extra transmembrane helices attributed to cyt cy and the assembly factor CcoH. The cyt cy is integral to SC, its cyt domain is mobile and conveys electrons to CIV differently than cyt c2. For the first time, this work establishes the structural characteristics of membrane-confined and membrane-external electron transport pathways of SCs in Gram-negative bacteria.

scholarly journals Mobile Cytochrome c2 and Membrane-Anchored Cytochrome cy Are Both Efficient Electron Donors to the cbb3- andaa3-Type Cytochrome cOxidases during Respiratory Growth of Rhodobacter sphaeroides

2001 ◽  
Vol 183 (6) ◽  
pp. 2013-2024 ◽  
Author(s):  
Fevzi Daldal ◽  
Sevnur Mandaci ◽  
Christine Winterstein ◽  
Hannu Myllykallio ◽  
Kristen Duyck ◽  
...  
Keyword(s):  
Electron Transport ◽  
Rhodobacter Sphaeroides ◽  
Rhodobacter Capsulatus ◽  
Electron Flow ◽  
Growth Conditions ◽  
Transport Pathways ◽  
Electron Carrier ◽  
Mobile Electron ◽  
Respiratory Growth ◽  
Respiratory Electron Transport

ABSTRACT We have recently established that the facultative phototrophic bacterium Rhodobacter sphaeroides, like the closely relatedRhodobacter capsulatus species, contains both the previously characterized mobile electron carrier cytochromec 2 (cyt c 2) and the more recently discovered membrane-anchored cytc y. However, R. sphaeroides cytc y, unlike that of R. capsulatus, is unable to function as an efficient electron carrier between the photochemical reaction center and the cyt bc 1complex during photosynthetic growth. Nonetheless, R. sphaeroides cyt c y can act at least in R. capsulatus as an electron carrier between the cytbc 1 complex and thecbb 3-type cyt c oxidase (cbb 3-Cox) to support respiratory growth. Since R. sphaeroides harbors both acbb 3-Cox and anaa 3-type cyt c oxidase (aa 3-Cox), we examined whetherR. sphaeroides cyt c y can act as an electron carrier to either or both of these respiratory terminal oxidases. R. sphaeroides mutants which lacked either cyt c 2 or cyt c y and either the aa 3-Cox or thecbb 3-Cox were obtained. These double mutants contained linear respiratory electron transport pathways between the cyt bc 1 complex and the cytc oxidases. They were characterized with respect to growth phenotypes, contents of a-, b-, andc-type cytochromes, cyt c oxidase activities, and kinetics of electron transfer mediated by cytc 2 or cyt c y. The findings demonstrated that both cyt c 2 and cytc y are able to carry electrons efficiently from the cyt bc 1 complex to either thecbb 3-Cox or theaa 3-Cox. Thus, no dedicated electron carrier for either of the cyt c oxidases is present in R. sphaeroides. However, under semiaerobic growth conditions, a larger portion of the electron flow out of the cytbc 1 complex appears to be mediated via the cytc 2-to-cbb 3-Coxand cytcy -to-cbb 3-Coxsubbranches. The presence of multiple electron carriers and cytc oxidases with different properties that can operate concurrently reveals that the respiratory electron transport pathways of R. sphaeroides are more complex than those ofR. capsulatus.

Contribution of leucine 85 to the structure and function of Saccharomyces cerevisiae iso-1 cytochrome c

2001 ◽  
Vol 79 (4) ◽  
pp. 517-524 ◽  
Author(s):  
Jonathan C Parrish ◽  
J Guy Guillemette ◽  
Carmichael JA Wallace
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Electron Transfer ◽  
Electron Transport ◽  
Cytochrome C ◽  
Transport Processes ◽  
Complex Iii ◽  
Side Chain ◽  
Inner Mitochondrial Membrane ◽  
And Function ◽  
First Time

Cytochrome c is a small electron-transport protein whose major role is to transfer electrons between complex III (cytochrome reductase) and complex IV (cytochrome c oxidase) in the inner mitochondrial membrane of eukaryotes. Cytochrome c is used as a model for the examination of protein folding and structure and for the study of biological electron-transport processes. Amongst 96 cytochrome c sequences, residue 85 is generally conserved as either isoleucine or leucine. Spatially, the side chain is associated closely with that of the invariant residue Phe82, and this interaction may be important for optimal cytochrome c activity. The functional role of residue 85 has been examined using six site-directed mutants of Saccharomyces cerevisiae iso-1 cytochrome c, including, for the first time, kinetic data for electron transfer with the principle physiological partners. Results indicate two likely roles for the residue: first, heme crevice resistance to ligand exchange, sensitive to both the hydrophobicity and volume of the side chain; second, modulation of electron-transport activity through maintenance of the hydrophobic character of the protein in the vicinity of Phe82 and the exposed heme edge, and possibly of the ability of this region to facilitate redox-linked conformational change.Key words: protein engineering, cytochrome c, structure-function relations, electron transfer, hydrophobic packing.

scholarly journals The High-Spin Heme bL Mutant Exposes Dominant Reaction Leading to the Formation of the Semiquinone Spin-Coupled to the [2Fe-2S]+ Cluster at the Qo Site of Rhodobacter capsulatus Cytochrome bc1

2021 ◽  
Vol 9 ◽  
Author(s):  
Marcin Sarewicz ◽  
Sebastian Pintscher ◽  
Łukasz Bujnowicz ◽  
Małgorzata Wolska ◽  
Artur Osyczka
Keyword(s):  
Electron Transfer ◽  
High Spin ◽  
Rhodobacter Capsulatus ◽  
Lipid Membrane ◽  
Proton Translocation ◽  
Complex Iii ◽  
Native Enzyme ◽  
Energetic Efficiency ◽  
Protonmotive Force ◽  
Back Electron Transfer

Cytochrome bc1 (mitochondrial complex III) catalyzes electron transfer from quinols to cytochrome c and couples this reaction with proton translocation across lipid membrane; thus, it contributes to the generation of protonmotive force used for the synthesis of ATP. The energetic efficiency of the enzyme relies on a bifurcation reaction taking place at the Qo site which upon oxidation of ubiquinol directs one electron to the Rieske 2Fe2S cluster and the other to heme bL. The molecular mechanism of this reaction remains unclear. A semiquinone spin-coupled to the reduced 2Fe2S cluster (SQo-2Fe2S) was identified as a state associated with the operation of the Qo site. To get insights into the mechanism of the formation of this state, we first constructed a mutant in which one of the histidine ligands of the iron ion of heme bLRhodobacter capsulatus cytochrome bc1 was replaced by asparagine (H198N). This converted the low-spin, low-potential heme into the high-spin, high-potential species which is unable to support enzymatic turnover. We performed a comparative analysis of redox titrations of antimycin-supplemented bacterial photosynthetic membranes containing native enzyme and the mutant. The titrations revealed that H198N failed to generate detectable amounts of SQo-2Fe2S under neither equilibrium (in dark) nor nonequilibrium (in light), whereas the native enzyme generated clearly detectable SQo-2Fe2S in light. This provided further support for the mechanism in which the back electron transfer from heme bL to a ubiquinone bound at the Qo site is mainly responsible for the formation of semiquinone trapped in the SQo-2Fe2S state in R. capusulatus cytochrome bc1.

scholarly journals The interaction between mitochondrial NADH-ubiquinone oxidoreductase and ubiquinol-cytochrome c oxidoreductase. Restoration of ubiquinone-pool behaviour

1978 ◽  
Vol 174 (3) ◽  
pp. 791-800 ◽  
Author(s):  
C Heron ◽  
C I Ragan ◽  
B L Trumpower
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Complex I ◽  
Mitochondrial Membrane ◽  
Complex Iii ◽  
Relative Mobility ◽  
Inner Mitochondrial Membrane ◽  
Ubiquinone Oxidoreductase ◽  
Nadh Ubiquinone Oxidoreductase ◽  
Ubiquinone 10

1. In the inner mitochondrial membrane, dehydrogenases and cytochromes appear to act independently of each other, and electron transport has been proposed to occur through a mobile pool of ubiquinone-10 molecules [Kröger & Klingenberg (1973) Eur. J. Biochem. 34, 358–368]. 2. Such behaviour can be restored to the interaction between purified Complex I and Complex III by addition of phospholipid and ubiquinone-10 to a concentrated mixture of the Complexes before dilution. 3. A model is proposed for the interaction of Complex I with Complex III in the natural membrane that emphasizes relative mobility of the Complexes rather than ubiquinone-10. Electron transfer occurs only through stoicheiometric Complex I-Complex III units, which, however, are formed and re-formed at rates higher than the rate of electron transfer.

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