The H+/site ratio of mitochondrial electron transport

M. D. Brand, B. Reynafarje, A. L. Lehninger

Research output: Contribution to journalArticle

Abstract

The number of H+ ejected during passage of 2e- through each energy conserving site of the mitochondrial respiratory chain (the H+/site ratio) was measured in three ways. In each case transmembrane movements of endogenous phosphate were minimized. Measurement of the uptake of weak acids during loading of mitochondria with Ca2+ demonstrated that 2.0 weak acid anions were accumulated per Ca2+ ion. Since 1.7 to 2.0 Ca2+ ions were taken up per site, these data correspond to an H+/site ratio of 3.5 to 4.0. More direct measurement of H+ ejection using the oxygen pulse technique demonstrated that the H+/site ratio was 3.0. In these experiments phosphate movements were prevented by addition of N ethylmaleimide to inhibit phosphate hydroxide antiport, by washing the mitochondria to remove endogenous phosphate, or by working at 5°C to reduce the rate of phosphate transport. When phosphate movements were allowed, H+/site ratios of 2.0 were observed. Measurement of the initial steady rates of oxygen consumption and H+ ejection following addition of substrate to aerobic, substrate limited mitochondria yielded H+/site ratios of 2.0, which were elevated to 4.0 when phosphate transport was prevented as described above. Previous determinations of the H+/site ratio were thus underestimates due to the unrecognized movements of endogenous phosphate; the results show that the H+/site ratio is at least 3.0 and may be as high as 4.0.

Original languageEnglish (US)
Pages (from-to)595-602
Number of pages8
JournalJournal of Cellular Physiology
Volume89
Issue number4
StatePublished - 1976

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Electron Transport
Phosphates
Mitochondria
Ions
Oxygen
Ethylmaleimide
Acids
Ion Transport
Substrates
Washing
Oxygen Consumption
Anions

ASJC Scopus subject areas

  • Cell Biology
  • Clinical Biochemistry
  • Physiology

Cite this

Brand, M. D., Reynafarje, B., & Lehninger, A. L. (1976). The H+/site ratio of mitochondrial electron transport. Journal of Cellular Physiology, 89(4), 595-602.

The H+/site ratio of mitochondrial electron transport. / Brand, M. D.; Reynafarje, B.; Lehninger, A. L.

In: Journal of Cellular Physiology, Vol. 89, No. 4, 1976, p. 595-602.

Research output: Contribution to journalArticle

Brand, MD, Reynafarje, B & Lehninger, AL 1976, 'The H+/site ratio of mitochondrial electron transport', Journal of Cellular Physiology, vol. 89, no. 4, pp. 595-602.
Brand MD, Reynafarje B, Lehninger AL. The H+/site ratio of mitochondrial electron transport. Journal of Cellular Physiology. 1976;89(4):595-602.
Brand, M. D. ; Reynafarje, B. ; Lehninger, A. L. / The H+/site ratio of mitochondrial electron transport. In: Journal of Cellular Physiology. 1976 ; Vol. 89, No. 4. pp. 595-602.
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