The Response of the Respiratory Chain and Adenine Nucleotide System to Oxidative Phosphorylation in Yeast Mitochondria

Abstract

Properties and functions of the respiratory chain and of the nucleotide system were studied in mitochondria from Saccharomyces carlsbergensis and compared with those in mitochondria from mammalian tissues. The composition of the respiratory chain showed a comparatively high content of DPN, ubiquinone, and cytochrome c. The failure of DPN to become reduced in the controlled state with any substrate confirms the absence of the first phosphorylation site. The redox states of the other components are controlled by the last two phosphorylation sites as in mammalian mitochondria. Substrates such as lactate, which feed hydrogen into the chain via cytochrome c, reduce ubiquinone in an energy‐dependent reverse electron transport. The mitochondrial content of nucleotides and of the 32P incorporating components was analysed. The mitochondria were found to have a similar equipment of nucleotides etc. as mammalian mitochondria. The phosphate transfer system in mitochondria was investigated. The phosphorylation rate of exogenous ADP is even at lower temperatures greater than that of endogenous ADP, in contrast to mammalian mitochondria. A specific exchange between exogenous and endogenous adenine nucleotides is found with similar properties as the exchange in mammalian mitochondria. Copyright © 1967, Wiley Blackwell. All rights reserved