The cytochrome bc1 complex from Rhodovulum sulfidophilum is a dimer with six quinones per monomer and an additional 6‐kDa component

Montoya, Guillermo; Kaat, Kai te; Rodgers, Simon; Nitschke, Wolfgang; Sinning, Irmgard

doi:10.1046/j.1432-1327.1999.00094.x

Cited by 15 publications

(24 citation statements)

References 65 publications

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“…2, spectra labeled WT mbs). The comparison of spectra taken on purified cytochrome bc 1 complex (17) indicated that the large majority of these additional heme species can be attributed to this enzyme (Fig. 2, bottom spectra).…”

Section: Identification Of Paramagnetic Species Arising From the Rcasmentioning

confidence: 96%

Structural and Functional Characterization of the Unusual Triheme Cytochrome Bound to the Reaction Center of Rhodovulum sulfidophilum

Alric

Tsukatani

Yoshida

et al. 2004

Journal of Biological Chemistry

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The cytochrome bound to the photosynthetic reaction center of Rhodovulum sulfidophilum presents two unusual characteristics with respect to the well characterized tetraheme cytochromes. This cytochrome contains only three hemes because it lacks the peptide motif CXXCH, which binds the most distal fourth heme. In addition, we show that the sixth axial ligand of the third heme is a cysteine (Cys-148) instead of the usual methionine ligand. This ligand exchange results in a very low midpoint potential (؊160 ؎ 10 mV). The influence of the unusual cysteine ligand on the midpoint potential of this distal heme was further investigated by site-directed mutagenesis. The midpoint potential of this heme is upshifted to ؉310 mV when cysteine 148 is replaced by methionine, in agreement with the typical redox properties of a His/Met coordinated heme. Because of the large increase in the midpoint potential of the distal heme in the mutant, both the native and modified high potential hemes are photooxidized at a redox poise where only the former is photooxidizable in the wild type. The relative orientation of the three hemes, determined by EPR measurements, is shown different from tetraheme cytochromes. The evolutionary basis of the concomitant loss of the fourth heme and the down-conversion of the third heme is discussed in light of phylogenetic relationships of the Rhodovulum species triheme cytochromes to other reaction center-associated tetraheme cytochromes.

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Section: Identification Of Paramagnetic Species Arising From the Rcasmentioning

confidence: 96%

Structural and Functional Characterization of the Unusual Triheme Cytochrome Bound to the Reaction Center of Rhodovulum sulfidophilum

Alric

Tsukatani

Yoshida

et al. 2004

Journal of Biological Chemistry

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“…The procedure has since been applied for isolation of cytochrome bc 1 complexes from α proteobacteria (32)(33)(34)(35)(36)(37)(38), firmicutes (39,40), and from mitochondria of animals (34), plants (41), fungi (34), Chlorophyta (42), and trypanosomes (EA Berry, L-S Huang, HA Avila, L Simpson, unpublished data).…”

Section: Purification Of Bc Complexesmentioning

confidence: 99%

“…Functional involvement is suggested by resolution and reconstitution experiments (101) and by site-directed mutagenesis (102). The bc 1 complex from Rhodovulum sulfidophilum contains, in addition to the three redox-center-bearing subunits, a 6-kDa protein with N-terminal sequence PDNTSNDDVLVPAS (38). This component could be removed by high detergent treatment, but this also removed the Rieske protein, monomerized the complex, and eliminated activity.…”

Section: Individual Protein Subunits Of the Cytochrome Bc 1 Complex Smentioning

confidence: 99%

Structure and Function of CytochromebcComplexes

Berry

Guergova-Kuras²,

Huang³

et al. 2000

Annu. Rev. Biochem.

472

461

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Key Words oxidoreductase, respiratory chain, electron transfer, crystallography, membrane protein s Abstract The cytochrome bc complexes represent a phylogenetically diverse group of complexes of electron-transferring membrane proteins, most familiarly represented by the mitochondrial and bacterial bc 1 complexes and the chloroplast and cyanobacterial b 6 f complex. All these complexes couple electron transfer to proton translocation across a closed lipid bilayer membrane, conserving the free energy released by the oxidation-reduction process in the form of an electrochemical proton gradient across the membrane. Recent exciting developments include the application of site-directed mutagenesis to define the role of conserved residues, and the emergence over the past five years of X-ray structures for several mitochondrial complexes, and for two important domains of the b 6 f complex. CONTENTS

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“…We have therefore performed an oriented EPR study on various states of the cytochrome bc 1 -complex. The enzyme purified from Rhodovulum sulfidophilum (18) was chosen for the experiments described below because of its high stability and an almost fully occupied Q o -site.…”

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A spectroscopic method for observing the domain movement of the Rieske iron–sulfur protein

Brugna

Rodgers

Schricker

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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The g-tensor orientation of the chemically reduced Rieske cluster in cytochrome bc1 complex from Rhodovulum sulfidophilum with respect to the membrane was determined in the presence and absence of inhibitors and in the presence of oxidized and reduced quinone in the quinol-oxidizing-site (Qo-site) by EPR on twodimensionally ordered samples. Almost identical orientations were observed when oxidized or reduced quinone, stigmatellin, or 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole was present. Occupancy of the Qo-site by myxothiazole induced appearance of a minority population with a substantially differing conformation and presence of E-␤-methoxyacrylate-stilbene significantly reduced the contribution of the major conformation observed in the other cases. Furthermore, when the oxidized iron-sulfur cluster was reduced at cryogenic temperatures by the products of radiolysis, the orientation of its magnetic axes was found to differ significantly from that of the chemically reduced center. The ''irradiation-induced'' conformation converts to that of the chemically reduced center after thawing of the sample. These results confirm the effects of Qo-site inhibitors on the equilibrium conformation of the Rieske iron-sulfur protein and provide evidence for a reversible redox-influenced interconversion between conformational states. Moreover, the data obtained with the iron-sulfur protein demonstrate that the conformation of ''EPR-inaccessible'' reduction states of redox centers can be studied by inducing changes of redox state at cryogenic temperatures. This technique appears applicable to a wide range of comparable electron transfer systems performing redox-induced conformational changes. T he cytochrome bc-complex is the only energy-coupling membrane-integral enzyme common to both photosynthetic and respiratory electron transport chains. In addition to three heme groups, the enzyme contains an unusual [2Fe2S] cluster, the so-called Rieske center. A key enzymatic feature of the complex is the bifurcation of the two electrons derived from oxidation of a quinol molecule at a catalytic site (the ''Q o -site'') into two distinct electron transfer chains within the complex. The Q o -site is positioned between a b-type heme and the [2Fe2S]-cluster of the Rieske iron-sulfur protein (ISP), and the ISP protein has been shown to play a decisive role in turnover at the site (1). Apart from the physiological quinone, the Q o -site binds several competitive and noncompetitive inhibitors of catalysis (mostly quinone analogs) such as stigmatellin, 5-(n-undecyl)-6-hydroxy-4,7-dioxobenzothiazole (UHDBT), myxothiazole, or E-␤-methoxyacrylate (MOA) stilbene.In the recent x-ray structure analyses of the mitochondrial cytochrome bc 1 complex (2-5), the Rieske protein was found in three distinct positions with respect to the remaining subunits of the enzyme, i.e., in a geometry positioning the of the enzyme during turnover, and a domain movement of the Rieske protein was implied as a prerequisite for efficient electron transfer (3-5). A deta...

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The cytochrome bc₁ complex from Rhodovulum sulfidophilum is a dimer with six quinones per monomer and an additional 6‐kDa component

Cited by 15 publications

References 65 publications

Structural and Functional Characterization of the Unusual Triheme Cytochrome Bound to the Reaction Center of Rhodovulum sulfidophilum

Structural and Functional Characterization of the Unusual Triheme Cytochrome Bound to the Reaction Center of Rhodovulum sulfidophilum

Structure and Function of CytochromebcComplexes

A spectroscopic method for observing the domain movement of the Rieske iron–sulfur protein

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