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Title: The H'+/O stoichiometry and control of mitochondrial respiration
Author: Murphy, Michael Patrick
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1987
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The control of mitochondrial respiration was reviewed and the control of electron flux through cytochrome oxidase, particularly the dependence of electron flux on Δψ and the redox state of the cytochrome-c pool was investigated. The elasticities of electron flux through cytochrome oxidase to Δψ and to ΔE_n across the complex were determined. It was shown that Δψ and ΔE_n have approximately equal control over electron flux through cytochrome oxidase under conditions similar to those found in vivo. The thermodyamic forces (ΔEn and Δp) across cytochrome oxidase were measured and thus its maximum possible q^+ /2e^- stoichiometry was estimated. This indicates that a q^+ /2e^- stoichiometry of 6 (corresponding to a H^+ /2e^- stoichiometry of 4) is thermodynamically impossible when Δp is greater than about 175mV. A method of measuring the q+ /O stoichiometry of the mitochondrial respiratory chain under conditions of high Δψ was developed. For mitochondria respiring on succinate the q^+ /O stoichiometry was about 2.75 when Δψ was high (170mV) and it increased to 6 as Δψ was lowered to about 85mV. This is the first direct evidence for a stoichiometry change in the mitochondrial respiratory chain. This technique was extended to measure separately the q^+ /2e^- stoichiometries of the cytochrome-bc_1 complex and cytochrome oxidase. The measured q^+ /2e^- stoichiometry of the cytochrome-bc_1 complex was between 1 and 1.25 and was invariant as Δψ was altered from 157mV to 85mV. The measured q+ /2e- stoichiometry of cytochrome oxidase decreased from 3.5 at low values of Δψ (120mV) to 1.5 at high values of Δψ (180mV).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biochemistry