CHANGES IN KINETICS OF ATP-SYNTHETASE AND IN CONCENTRATIONS OF ADENINE-NUCLEOTIDES IN GROUND-SQUIRREL LIVER-MITOCHONDRIA DURING HIBERNATION

1. 1. Oligomycin titration studies have shown that H+-ATPase of ground squirrel liver mitochondria is a rate-limiting stage of oxidative phosphorylation in hibernating animals. 2. 2. H+-ATPase from both ground squirrel liver and bovine heart mitochondria has the regulatory site for binding ATP and ADP (KM ∼ 1 mM). The affinity of this site for adenine nucleotides increases approximately 2-fold in arousing ground squirrels. 3. 3. A similar increase in the affinity of the regulatory site of bovine heart H+-ATPase was achieved by preincubating SMP with ADP in the absence of all other substrates. 4. 4. An approximate 5-fold decrease of intramitochondrial ATP + ADP concentration in hibernating ground squirrels has been revealed. 5. 5. It is suggested that the decrease in the affinity of the regulatory site of H+-ATPase for ATP and ADP with a simultaneous decline of their total intramitochondrial concentration is essential for limiting the rate of oxidative phosphorylation in hibernating ground squirrels. © 1990.