Physiological Uncoupling of Mitocondria from Different Yeast Species

Abstract

A slow rate of oxygen consumption and a high transmembrane potential increase the rate of reactive oxygen species production (ROS). ROS in turn covalently attach and destroy membranes, proteins and carbohydrates. In order to avoid ROS-mediated damage, mitocondria contain diverse uncoupling mechanisms which accelerate the respiratory chain and lower the transmembrane potential. Two uncoupling mechanisms have been proposed. There are proteins that dissipate proton gradients either specifically (uncoupling proteins) or unspecifically (channels). A second mechanism is the activation of redox proteins that do not contribute to the proton gradient and therefore are sensitive to the ΔpH. In addition, pumps may suffer intrinsic uncoupling (slipping). In different yeast species, a number of mitocondrial uncoupling systems has been identified. Saccharomyces cerevisiae and Debaryomyces hansenii express highly regulated mitocondrial unspecific channels. A UCP has been described in Yarrowia lipolytica. Non-pumping alternative oxido-reductases exist in the branched respiratory chain from Y. lipolytica. The variety of energy dissipating systems in eukaryote species is probably designed to control ROS production in the different environments where each species lives.