Effects of subunit V antibodies on the topology of the subunit and the activity of beef heart cytochrome-c oxidase

1988 ◽  
Vol 66 (11) ◽  
pp. 1210-1217 ◽  
Author(s):  
Jo A. Freedman ◽  
Bryan Leece ◽  
Christopher E. Cooper ◽  
Peter Nicholls ◽  
Samuel H. P. Chan
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Redox State ◽  
Quantitative Comparison ◽  
Beef Heart ◽  
Specific Antibodies ◽  
Antibody Preparations

Redox-sensitive epitopes on subunit V of beef heart cytochrome-c oxidase were demonstrated previously using polyclonal subunit-specific antibodies raised in rabbits. The antibodies only slightly inhibited electron transfer, and the accessibility of their epitopes depended on the presence of a membrane and on the redox state of the oxidase. The present paper describes additional preparations of antibodies raised against subunit V. These antibodies have an even higher subunit specificity, they are more than three times as inhibitory against electron transfer, and their binding does not require a membrane. Moreover, the redox-sensitive nature of their binding to detergent-dispersed oxidase is sensitive to the method of its isolation. We discuss inferences that can be drawn from a detailed quantitative comparison of the interactions of the two antibody preparations with the antigen in different environments. The techniques used in the comparison can be used to examine other perturbants of the oxidase as to their effects on specific segments of the enzyme.

Control of proteoliposomal cytochrome c oxidase: the partial reactions

1990 ◽  
Vol 68 (9) ◽  
pp. 1135-1141 ◽  
Author(s):  
Peter Nicholls
Keyword(s):  
Electron Transfer ◽  
Steady State ◽  
Membrane Potential ◽  
Cytochrome C ◽  
Cytochrome Oxidase ◽  
Cytochrome C Oxidase ◽  
Redox State ◽  
Ph Gradient ◽  
Transfer Model ◽  
State Reduction

The steady-state spectroscopic behaviour and the turnover of cytochrome c oxidase incorporated into proteoliposomes have been investigated as functions of membrane potential and pH gradient. The respiration rate is almost linearly dependent on [cytochrome c2+] at high flux, but while the cytochrome a redox state is always dependent on the [cytochrome c2+] steady state, it reaches a maximum reduction level less than 100% in each case. The maximal aerobic steady-state reduction level of cytochrome a is highest in the presence of valinomycin and lowest in the presence of nigericin. The proportion of [cytochrome c2+] required to achieve 50% of maximal reduction of cytochrome a varies with the added ionophores; the apparent redox potential of cytochrome a is most positive in the fully decontrolled system (plus valinomycin and nigericin). At low levels of cytochrome a reduction, the rate of respiration is no longer a linear function of [cytochrome c2+], but is dependent upon the redox state of both cytochromes a and c. That is, proteoliposomal oxidase does not follow Smith–Conrad kinetics at low cytochrome c reduction levels, especially in the controlled states. The control of cytochrome oxidase turnover by ΔpH and by ΔΨ can be explained either by an allosteric model or by a model with reversed electron transfer between the binuclear centre and cytochrome a. Other evidence suggests that the reversed electron transfer model may be the correct one.Key words: proteoliposomes, cytochrome c, cytochrome oxidase, membrane potential, pH gradient, cytochrome a, electron transfer.

Covalent complex between yeast cytochrome c and beef heart cytochrome c oxidase which is active in electron transfer

Biochemistry ◽  
1981 ◽  
Vol 20 (24) ◽  
pp. 7046-7053 ◽  
Author(s):  
Stephen D. Fuller ◽  
Victor M. Darley-Usmar ◽  
Roderick A. Capaldi
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Beef Heart ◽  
Covalent Complex

scholarly journals Probing the high-affinity site of beef heart cytochrome c oxidase by cross-linking

1996 ◽  
Vol 315 (3) ◽  
pp. 909-916 ◽  
Author(s):  
Francesco MALATESTA ◽  
Giovanni ANTONINI ◽  
Flavia NICOLETTI ◽  
Alessandro GIUFFRÈ ◽  
Emilio D'ITRI ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Beef Heart ◽  
State Reduction ◽  
High Affinity ◽  
Disulphide Bond Formation ◽  
High Affinity Site ◽  
Low Ionic Strength ◽  
Covalent Complex

A covalent complex between cytochrome c oxidase and Saccharomyces cerevisiae iso-1-cytochrome c (called caa3) has been prepared at low ionic strength. Subunit III Cys-115 of beef heart cytochrome c oxidase cross-links by disulphide bond formation to thionitrobenzoate-modified yeast cytochrome c, a derivative shown to bind into the high-affinity site for substrate [Fuller, Darley-Usmar and Capaldi (1981) Biochemistry 20, 7046–7053]. Stopped-flow experiments show that (1) covalently bound yeast cytochrome c cannot donate electrons to cytochrome oxidase, whereas oxidation of exogenously added cytochrome c and electron transfer to cytochrome a are only slightly affected; (2) the steady-state reduction levels of cytochrome c and cytochrome a in the covalent complex caa3 are higher than those found in the native aa3 enzyme. However, (3) Km and Vmax values obtained from the non-linear Eadie–Hofstee plots are very similar in both caa3 and aa3. The results imply that cytochrome c bound to the high-affinity site is not in a configuration optimal for electron transfer.

scholarly journals Cloning and sequencing of the cDNA for a 13th different subunit (IHQ) of beef heart cytochrome c oxidase

1989 ◽  
Vol 264 (28) ◽  
pp. 16858-16861
Author(s):  
R Lightowlers ◽  
S Takamiya ◽  
R Wessling ◽  
M Lindorfer ◽  
R A Capaldi
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Beef Heart ◽  
Cloning And Sequencing
Sign in / Sign up

Export Citation Format

Share Document