title: Physiological uncoupling of mitochondrial oxidative phosphorylation. Studies in different yeast species.
abstract: Under non-phosphorylating conditions a high proton transmembrane gradient inhibits the rate of oxygen consumption mediated by the mitochondrial respiratory chain (state IV). Slow electron transit leads to production of reactive oxygen species (ROS) capable of participating in deleterious side reactions. In order to avoid overproducing ROS, mitochondria maintain a high rate of O(2) consumption by activating different exquisitely controlled uncoupling pathways. Different yeast species possess one or more uncoupling systems that work through one of two possible mechanisms: i) Proton sinks and ii) Non-pumping redox enzymes. Proton sinks are exemplified by mitochondrial unspecific channels (MUC) and by uncoupling proteins (UCP). Saccharomyces. cerevisiae and Debaryomyces hansenii express highly regulated MUCs. Also, a UCP was described in Yarrowia lipolytica which promotes uncoupled O(2) consumption. Non-pumping alternative oxido-reductases may substitute for a pump, as in S. cerevisiae or may coexist with a complete set of pumps as in the branched respiratory chains from Y. lipolytica or D. hansenii. In addition, pumps may suffer intrinsic uncoupling (slipping). Promising models for study are unicellular parasites which can turn off their aerobic metabolism completely. The variety of energy dissipating systems in eukaryote species is probably designed to control ROS production in the different environments where each species lives.
authors.affiliation: Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Ciudad Universitaria, Apdo. Postal 70-242, Mexico City, México DF, Mexico.
authors.forename: Sergio
authors.initials: S
authors.lastname: Guerrero-Castillo
authors.forename: Daniela
authors.initials: D
authors.lastname: Araiza-Olivera
authors.forename: Alfredo
authors.initials: A
authors.lastname: Cabrera-Orefice
authors.forename: Juan
authors.initials: J
authors.lastname: Espinasa-Jaramillo
authors.forename: Manuel
authors.initials: M
authors.lastname: Gutiérrez-Aguilar
authors.forename: Luís A
authors.initials: LA
authors.lastname: Luévano-Martínez
authors.forename: Armando
authors.initials: A
authors.lastname: Zepeda-Bastida
authors.forename: Salvador
authors.initials: S
authors.lastname: Uribe-Carvajal
mesh_terms: D055165:Debaryomyces / Q000378:metabolism; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010088:Oxidoreductases / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D004718:Saccharomycetales / Q000378:metabolism*; D000071256:Uncoupling Protein 1; D025062:Yarrowia / Q000378:metabolism
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; D017382:Reactive Oxygen Species; D000071256:Uncoupling Protein 1; D010088:Oxidoreductases