Temperature Dependence of ADP/ATP Translocation in Mitochondria

Abstract

The temperature dependence of the adenine nucleotide exchange in mitochondria has been determined by employing a rapid mixing, quenching and sampling apparatus and the inhibitor quench‐back exchange method. Thus the exchange is resolved down to 0.1 s. Rates are evaluated from accumulating the time‐dependent progress at about 10 points. The exchange rate in liver mitochondria was determined from –10°C to +10°C in the presence of 20% glycol, from 0°C to 25°C, and from 20°C to 40°C under partial inhibition by carboxyatractylate. The total range between –10°C to + 40°C has only one temperature break at 13°C. From the Arrhenius plot between –10°C to +13°C, EA∼ 140 kJ and above 13°C, EA∼ 56 kJ is evaluated, corresponding to a Q10 of 8 and 2 respectively. In beef heart mitochondria the exchange rate was measured between 0°C and 20°C, and between 15°C and 30°C under partial inhibition with carboxyatractylate. There is a temperature break around 14°C with EA∼ 143 kJ between 0°C and 14°C and EA∼ 60 kJ from 15°C to 30°C. The extrapolated translocation rates at 37°C are 500 and 1800 μmol min−1 (g protein)−1 for rat liver and for beef heart mitochondria respectively. The temperature break is suggested to reflect a conformation change since there is no reversed break at low temperature, the temperature break changes in sonic particles and no lipid phase transition at 14°C in mitochondria has been reported. Copyright © 1982, Wiley Blackwell. All rights reserved