Structure and function of the chloroplast cytochrome bf complex

O’Keefe, Daniel P.

doi:10.1007/bf00035448

Cited by 32 publications

(4 citation statements)

References 124 publications

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“…The helix packing is likely to be somewhat variable, as the cross-sectional area per transmembrane helix varies in Table 1 from 0.73 to 2 nm2, the average being -1.4 nm2. However, proteins with smaller hydrophobic volumes, such as cytochromef (45,46) and gramicidin (53), might not bar diffusional access in the same way. The molecular dimensions and lateral diffusional properties of gramicidin at low gramicidin concentrations are very similar to those of lipid molecules (53), and, thus, gramicidin might not constitute an impenetrable protein domain in the absence of aggregation.…”

Section: Estimation Of Lateral Diffusion Coefficientmentioning

confidence: 99%

Effect of integral membrane proteins on the lateral mobility of plastoquinone in phosphatidylcholine proteoliposomes

Blackwell

Whitmarsh

1990

Biophysical Journal

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PYRENE FLUORESCENCE QUENCHING BY PLASTOQUINONE WAS USED TO ESTIMATE THE RATE OF PLASTOQUINONE LATERAL DIFFUSION IN SOYBEAN PHOSPHATIDYLCHOLINE PROTEOLIPOSOMES CONTAINING THE FOLLOWING INTEGRAL MEMBRANE PROTEINS: gramicidin D, spinach cytochrome bf complex, spinach cytochrome f, reaction centers from Rhodobacter sphaeroides, beef heart mitochondrial cytochrome bc(1), and beef heart mitochondrial cytochrome oxidase. The measured plastoquinone lateral diffusion coefficient varied between 1 and 3 . 10(-7) cm(2) s(-1) in control liposomes that lacked protein. When proteins were added, these values decreased: a 10-fold decrease was observed when 16-26% of the membrane surface area was occupied by protein for all the proteins but gramicidin. The larger protein complexes (cytochrome bf, Rhodobacter sphaeroides reaction centers, cytochrome bc(1), and cytochrome oxidase), whose hydrophobic volumes were 15-20 times as large as that of cytochrome f and the gramicidin transmembrane dimer, were 15-20 times as effective in decreasing the lateral-diffusion coefficient over the range of concentrations studied. These proteins had a much stronger effect than that observed for bacteriorhodopsin in fluorescence photobleaching recovery measurements. The effect of high-protein concentrations in gramicidin proteoliposomes was in close agreement with fluorescence photobleaching measurements. The results are compared with the predictions of several theoretical models of lateral mobility as a function of integral membrane concentration.

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Section: Estimation Of Lateral Diffusion Coefficientmentioning

confidence: 99%

Effect of integral membrane proteins on the lateral mobility of plastoquinone in phosphatidylcholine proteoliposomes

Blackwell

Whitmarsh

1990

Biophysical Journal

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“…[1][2][3][4][5][6][7] These electron transfer events are linked to proton translocation across the low dielectric membrane that generates a proton electrochemical potential gradient of approximately 250 mV, positive on the p-or lumen side of the membrane. A detailed understanding of charge transfer and movement of lipophilic quinone across the membrane in the b 6 f complex requires information derived from structure analysis.…”

Section: Introductionmentioning

confidence: 99%

Structure of the Cytochrome b6f Complex: Quinone Analogue Inhibitors as Ligands of Heme cn

Yamashita

Zhang

Cramer

2007

Journal of Molecular Biology

124

209

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A native structure of the cytochrome b(6)f complex with improved resolution was obtained from crystals of the complex grown in the presence of divalent cadmium. Two Cd(2+) binding sites with different occupancy were determined: (i) a higher affinity site, Cd1, which bridges His143 of cytochrome f and the acidic residue, Glu75, of cyt b(6); in addition, Cd1 is coordinated by 1-2 H(2)O or 1-2 Cl(-); (ii) a second site, Cd2, of lower affinity for which three identified ligands are Asp58 (subunit IV), Glu3 (PetG subunit) and Glu4 (PetM subunit). Binding sites of quinone analogue inhibitors were sought to map the pathway of transfer of the lipophilic quinone across the b(6)f complex and to define the function of the novel heme c(n). Two sites were found for the chromone ring of the tridecyl-stigmatellin (TDS) quinone analogue inhibitor, one near the p-side [2Fe-2S] cluster. A second TDS site was found on the n-side of the complex facing the quinone exchange cavity as an axial ligand of heme c(n). A similar binding site proximal to heme c(n) was found for the n-side inhibitor, NQNO. Binding of these inhibitors required their addition to the complex before lipid used to facilitate crystallization. The similar binding of NQNO and TDS as axial ligands to heme c(n) implies that this heme utilizes plastoquinone as a natural ligand, thus defining an electron transfer complex consisting of hemes b(n), c(n), and PQ, and the pathway of n-side reduction of the PQ pool. The NQNO binding site explains several effects associated with its inhibitory action: the negative shift in heme c(n) midpoint potential, the increased amplitude of light-induced heme b(n) reduction, and an altered EPR spectrum attributed to interaction between hemes c(n) and b(n). A decreased extent of heme c(n) reduction by reduced ferredoxin in the presence of NQNO allows observation of the heme c(n) Soret band in a chemical difference spectrum.

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“…Information bearing on the existence of dimeric states of the mitochondrial bc\ and chloroplast bff complexes was previously reviewed (von Jagow & Sebald, 1980; O'Keefe, 1988). The first indications for the existence of a dimeric cytochrome bc\ complex extractable from the membrane in a dimeric form came from the following: (i) studies on the cytochrome b of fungal (Neurospora crassa) mitochondria with Mr = 30 000 on SDS-PAGE and M, = 55 000-63 000 determined by size-exclusion chromatography or ultracentrifugation (Weiss, 1976); the ©…”

mentioning

confidence: 99%

Characterization of the Chloroplast Cytochrome b6f Complex as a Structural and Functional Dimer

Huang¹,

Everly²,

Cheng³

et al. 1994

Biochemistry

133

100

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Size analysis of the cytochrome bdcomplex by FPLC Superose-12 chromatography and Blue Native PAGE indicated a predominantly dimeric component with M, = (1.9-2.5) X lo5. The true dimer molecular weight including bound lipid, but not detergent, was estimated to be 2.3 X lo5. Size and shape analysis by negative-stain single-particle electron microscopy indicated that the preparation of dimeric complexes contains a major population that has a protein cross section 40% larger than the monomer, binds more negative stain, and has a geometry with a distinct 2-fold axis of symmetry compared to the monomeric complex. The dimeric species is more stable at higher ionic strength with respect to conversion to the monomeric species. SDS-PAGE of monomer and dimer preparations indicated that both contain the four major polypeptides in approximately equal stoichiometry and also contain thepetG M, 4000 subunit. One bound chlorophyll a per monomer, part of the bound lipid, is present in monomer and dimer. The in vitro electron-transport activity (decyl-PQHz -PC-ferricyanide) of the separated dimer was comparable to that of the isolated bdcomplex and was 4-5-fold greater than that of the monomer preparation, whose activity could be attributed to residual dimer. No difference in the properties of the dimer and monomer was detected by SDS-PAGE or redox difference spectrophotometry that could account for the difference in activities. However, the concentration of the Rieske [2Fe-2S] center was found by EPR analysis of the g , = 1.90 signal to be lower in the monomer fraction by a factor of 3.5 relative to the dimer. The presence of active dimer at high levels in the detergent-extracted bdcomplex, the absence of activity in the monomer, and the absence of a monomer preparation that is not degraded in its spectral properties and activity suggest that the simplest inference is that the dimer is the active complex in the membrane. The possibility that cytochrome b d and bcl are primitive trans-membrane-signaling complexes is noted.The cytochrome bsf complex is one of three integral membrane protein complexes involved in electron transport in membranes that carry out oxygenic photosynthesis. The bsfcomplex occupies an electrochemically central position in the noncyclic electron-transport chain, accepting electrons from the photosystem I1 reaction center that is associated with 0 2 evolution, and donating them to the photosystem I reaction center that reduces ferredoxin and nicotinamide adenine dinucleotide phosphate (NADP+). The bsfcomplex bears many similarities to the cytochrome bcl complex of the

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Structure and function of the chloroplast cytochrome bf complex

Cited by 32 publications

References 124 publications

Effect of integral membrane proteins on the lateral mobility of plastoquinone in phosphatidylcholine proteoliposomes

Effect of integral membrane proteins on the lateral mobility of plastoquinone in phosphatidylcholine proteoliposomes

Structure of the Cytochrome b6f Complex: Quinone Analogue Inhibitors as Ligands of Heme cn

Characterization of the Chloroplast Cytochrome b6f Complex as a Structural and Functional Dimer

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