Effects of K+ and other monovalent cations on yeast mitochondria

In mitochondria from Saccharomyces cerevisiae and in the presence of ethanol or NADH, K+ or Na+ increased the rate of O2 uptake in states 3 and uncoupled as well as in sonicated mitochondria. The respiratory control, the ADP:O ratio and the synthesis of ATP also increased. ATP hydrolysis by sonicated mitochondria increased depending on the cation added as follows: K+ = NH4+ = Rb+ Na+ Li+. This correlated with the ionic radii of the cations. Monovalent cations increased the activity of: 1) F1F0ATPase which was sensitive to cation size and 2) complex I of the respiratory chain, which seemed to regulate the rate of oxidative phosphorylation, but did not discriminate between K+ or Na+.