Coupling/Uncoupling Reversibility in Isolated Mitochondria from <i>Saccharomyces cerevisiae</i>

Abstract

The yeast Saccharomyces cerevisiae uses fermentation as the preferred pathway to obtain ATP and requires the respiratory chain to re-oxidize the NADH needed for activity of Glyceraldehyde-3-phosphate. This process is favored by uncoupling of oxidative phosphorylation (OxPhos), which is at least partially controlled by the mitochondrial unspecific pore (ScMUC). When mitochondrial ATP synthesis is needed as in the diauxic phase or during mating, a large rise in Ca2+ concentration ([Ca2+]) closes ScMUC, coupling OxPhos. In addition, ScMUC opening/closing is mediated by the ATP/ADP ratio, which indicates cellular energy needs. Here, opening and closing of ScMUC was evaluated in isolated mitochondria from S. cerevisiae at different incubation times and in the presence of different ATP/ADP ratios or varying [Ca2+]. Measurements of the rate of O2 consumption, mitochondrial swelling, transmembrane potential and ROS generation were conducted. It was observed that ScMUC opening was reversible, a high ATP/ADP ratio promoted opening and [Ca2+] closed ScMUC even after several minutes of incubation in the open state. In the absence of ATP synthesis, closure of ScMUC resulted in an increase in ROS.

Keywords

• physiological uncoupling
• yeast mitochondria
• mitochondrial permeability transition reversibility
• <i>_Sc</i>MUC
• Ca²⁺