The "B space" of mitochondrial phosphorylation |
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Authors: | Chinopoulos Christos |
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Affiliation: | Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary. chinopoulos.christos@eok.sote.hu |
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Abstract: | It was recently shown that, in progressively depolarizing mitochondria, the F(0) -F(1) ATP synthase and the adenine nucleotide translocase (ANT) may change directionality independently from each other (Chinopoulos et al. [2010] FASEB J. 24:2405). When the membrane potentials at which these two molecular entities reverse directionality, termed reversal potential (Erev), are plotted as a function of matrix ATP/ADP ratio, an area of the plot is bracketed by the Erev_ATPase and the Erev_ANT, which we call "B space". Both reversal potentials are dynamic, in that they depend on the fluctuating values of the participating reactants; however, Erev_ATPase is almost always more negative than Erev_ANT. Here we review the conditions that define the boundaries of the "B space". Emphasis is placed on the role of matrix substrate-level phosphorylation, because during metabolic compromise this mechanism could maintain mitochondrial membrane potential and prevent the influx of cytosolic ATP destined for hydrolysis by the reversed F(0) -F(1) ATP synthase. |
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