scholarly journals Reconstitution of cytochrome c oxidase in phospholipid vesicles containing polyvinylic polymers

1989 ◽  
Vol 257 (3) ◽  
pp. 783-787 ◽  
Author(s):  
P Sarti ◽  
G Antonini ◽  
F Malatesta ◽  
B Vallone ◽  
S Villaschi ◽  
...  
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Functional Characterization ◽  
Respiratory Control ◽  
Phospholipid Vesicles ◽  
Lipid Phase ◽  
Protein Orientation ◽  
Highly Hydrophobic ◽  
Polymer Interaction

Cytochrome c oxidase was reconstituted in phospholipid vesicles in the presence of highly hydrophobic poly(vinyl alkanoate) polymers. Electron-microscopy observations demonstrated that polymer interaction with the lipid phase induces vesicles to adopt smaller diameters than those typical of standard proteoliposomes. Functional characterization of these polymer-proteoliposome structures indicates that the reconstitution of the enzyme proceeds efficiently without causing either scrambling of the protein orientation in the membrane or loss of respiratory control. A clear dependence of respiratory control ratio on vesicle size was also demonstrated, which is in agreement with a previous model proposed for control of activity of cytochrome c oxidase vesicles [Brunori, Sarti, Colosimo, Antonini, Malatesta, Jones & Wilson (1985) EMBO J. 4, 2365-2368].

scholarly journals Electron microscopy of cytochrome c oxidase-containing proteoliposomes: imaging analysis of protein orientation and monomer-dimer behaviour

1993 ◽  
Vol 292 (3) ◽  
pp. 933-946 ◽  
Author(s):  
M Tihova ◽  
B Tattrie ◽  
P Nicholls
Keyword(s):  
Electron Microscopy ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Respiratory Control ◽  
Fracture Plane ◽  
Aggregation State ◽  
Protein Orientation ◽  
Small Areas ◽  
Probable Presence ◽  
Two Sides

1. Cytochrome c oxidase-containing vesicles were prepared by cholate dialysis using bovine heart cytochrome c oxidase with egg and dioleoylphosphatidylcholine/dioleoylphosphatidylethanolamines (1:1, w/w) at two ratios of phospholipid to protein (25 mg/mg and 10 mg/mg). With each mixture, one or two (FII, FIII) fractions with mostly outward-facing cytochrome aa3 were separated from a fraction (FI) containing mostly inward-facing enzyme and protein-free liposomes by DEAE-Sephacel chromatography. 2. FII and FIII fractions from egg phospholipid mixtures had 60-80% outward-facing enzyme; FII and FIII fractions from dioleoyl phospholipids showed 50-70% outward-facing enzyme. Egg and dioleoyl phospholipid mixtures maintained good respiratory control ratios (8-13) only at the higher lipid/protein ratios. 3. Platinum/carbon replicas of freeze-fractured vesicle surfaces were subjected to image analysis. The results showed two types of membrane projection with average heights of 7.5 nm and 3.5 nm from the fracture plane. The former were more numerous on the convex faces. Calculated areas of the projections indicated the probable presence of both enzyme dimers and higher aggregates. Oxidase dimers may have membrane areas of 70-80 nm2 at the high (7.5 nm) side and 40-50 nm2 on the low (3.5 nm) side. 4. Proteoliposomes prepared with enzyme depleted of subunit III contained predominantly much smaller projecting areas. These probably represent monomers with high side areas of 35-40 nm2 and low side areas of 20-25 nm2. Electron microscopy thus directly confirms the predicted change of aggregation state resulting from subunit depletion. 5. The results are compared with those from two-dimensional crystals. Assuming that the high and low projections are two sides of one family of transmembrane molecules, a total length of 11 nm matches 11-12 nm lengths obtained by crystallography. Our membrane areas match the areas obtained in earlier ‘crystal’ studies better than the small areas obtained recently by electron cryomicroscopy.

scholarly journals The effect of non-esterified fatty acids on the proton-pumping cytochrome c oxidase reconstituted into liposomes

1988 ◽  
Vol 254 (1) ◽  
pp. 139-145 ◽  
Author(s):  
N Labonia ◽  
M Müller ◽  
A Azzi
Keyword(s):  
Fatty Acids ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Respiratory Control ◽  
Proton Pumping ◽  
Phospholipid Vesicles ◽  
Proton Permeability ◽  
Enzyme Preparations ◽  
Esterified Fatty Acids ◽  
Subunit Iii

Bovine heart cytochrome c oxidase was reconstituted in phospholipid vesicles, and the effect of different non-esterified fatty acids (NEFA) was studied on its proton pump and on the proton permeability of the vesicles. Neither parameter appeared to be affected by concentrations of NEFA known to uncouple oxidative phosphorylation (10 microM). Also the permeability for K+ was not affected by them. The fatty acids caused an increase in the rate of electron transfer in the absence, but not in the presence, of uncoupler and/or valinomycin [diminution of the respiratory-control index (RCI)]. The RCI of 8.7-7.5 was decreased to about 4.5 in the presence of 0.27-10 microM-NEFA. Oleic acid was not effective at the above concentrations. Subunit III-depleted enzyme preparations gave vesicles with an RCI of about 5.5, which was decreased to 4.5 in the presence of NEFA. With both native and subunit III-depleted oxidase the RCI was never decreased to the value of 1 by NEFA, as happens with classical protonophores.

scholarly journals Dynamics of proteoliposome formation. Intermediate states during detergent dialysis

1987 ◽  
Vol 246 (3) ◽  
pp. 737-744 ◽  
Author(s):  
J M Wrigglesworth ◽  
M S Wooster ◽  
J Elsden ◽  
H J Danneel
Keyword(s):  
Electron Microscopy ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Protein Conformation ◽  
Respiratory Control ◽  
Molar Ratio ◽  
Gel Chromatography ◽  
Protein Orientation ◽  
Intermediate States ◽  
Small Unilamellar Vesicles

1. The intermediate structures formed during dialysis of mixtures of cholate, phospholipid and cytochrome c oxidase were analysed by gel chromatography and electron microscopy. Measurements of trapped phosphate and the degree of respiratory control were used to assess the integrity of the vesicular structures formed. Protein orientation in the bilayer was monitored by the accessibility of cytochrome c to cytochrome c oxidase. 2. The results indicate that proteoliposome formation by the detergent-dialysis procedure takes place in three distinct stages. In the first stage, cholate/phospholipid and cholate/phospholipid/protein micelles coexist in solution and grow in size as the detergent is slowly removed. At a detergent/phospholipid molar ratio of about 0.2, micelle fusion results in the formation of large bilayer aggregates permeable to both phosphate and cytochrome c. It is at this stage that cytochrome c oxidase is incorporated into the bilayer. In the final stage of dialysis the bilayer sheets fragment into small unilamellar vesicles. 3. The orientation of membrane protein in the final vesicles appears to be determined by the effect of protein conformation on the initial curvature of the bilayer sheets during the fragmentation process.

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