Most of the energy found in food is converted in our cells into ATP, a versatile energy carrier that enables many biochemical reactions. This energy conversion takes place in cellular structures termed mitochondria, from where the newly synthesised ATP is exported and distributed in the entire cell for use.
The significance of the cristae membrane organization, in the mitochondria, for these energy conversion processes has been unclear. In a recent report, an international team including researchers from the Department of Biochemistry and Biophysics propose a solution to this long-standing question.
In the current study, a genetically engineered pH sensor was placed at specific locations within the mitochondrial membranes, allowing to estimate local pH values within this organelle in living cells. Correct localization of the pH sensors was verified by fluorescence and electron microscopy analysis. Surprisingly, the measured pH gradient was very small and not sufficient to allow for ATP production in a minimal system using purified ATP synthase embedded in membrane vesicles. Moreover, the measured pH values were hardly permitting ATP synthesis even under thermodynamically sufficient conditions.
“At first, the data were quite confusing despite we were confident that our measurements were correct”, says Martin Ott, a corresponding author of this study. “But then our collaboration partners at the University of Bern made the observation that it only needs an active proton pump from the respiratory chain in the minimal system for it to work.
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