title: Oxidative phosphorylation in Debaryomyces hansenii: physiological uncoupling at different growth phases.
abstract: Physiological uncoupling of mitochondrial oxidative phosphorylation (OxPhos) was studied in Debaryomyces hansenii. In other species, such as Yarrowia lipolytica and Saccharomyces cerevisiae, OxPhos can be uncoupled through differential expression of branched respiratory chain enzymes or by opening of a mitochondrial unspecific channel (ScMUC), respectively. However D. hansenii mitochondria, which contain both a branched respiratory chain and a mitochondrial unspecific channel (DhMUC), selectively uncouple complex I-dependent rate of oxygen consumption in the stationary growth phase. The uncoupled complex I-dependent respiration was only 20% of the original activity. Inhibition was not due to inactivation of complex I, lack of protein expression or to differential expression of alternative oxidoreductases. Furthermore, all other respiratory chain activities were normal. Decrease of complex I-dependent respiration was due to NAD(+) loss from the matrix, probably through an open of DhMUC. When NAD(+) was added back, coupled complex I-activity was recovered. NAD(+) re-uptake was independent of DhMUC opening and seemed to be catalyzed by a NAD(+)-specific transporter, which was sensitive to bathophenanthroline, bromocresol purple or pyridoxal-5'-phosphate as described for S. cerevisiae mitochondrial NAD(+) transporters. Loss of NAD(+) from the matrix through an open MUC is proposed as an additional mechanism to uncouple OxPhos.
authors.affiliation: Dept of Molecular Genetics, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Alfredo
authors.initials: A
authors.lastname: Cabrera-Orefice
authors.affiliation: Dept of Molecular Genetics, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Sergio
authors.initials: S
authors.lastname: Guerrero-Castillo
authors.affiliation: Facultad de Medicina, Programa de Posgrado en Ciencias Médicas, Odontológicas y de la Salud, Universidad Nacional Autónoma de México, Mexico City, Mexico.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Díaz-Ruíz
authors.affiliation: Dept of Molecular Genetics, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico City, Mexico. Electronic address: suribe@ifc.unam.mx.
authors.forename: Salvador
authors.initials: S
authors.lastname: Uribe-Carvajal
mesh_terms: D019069:Cell Respiration / Q000235:genetics; D055165:Debaryomyces / Q000235:genetics / Q000254:growth & development*; D004579:Electron Transport / Q000235:genetics*; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D009243:NAD / Q000378:metabolism; D010085:Oxidative Phosphorylation; D010088:Oxidoreductases / Q000096:biosynthesis / Q000378:metabolism; D010101:Oxygen Consumption; D012441:Saccharomyces cerevisiae
chemical_list: D009243:NAD; D010088:Oxidoreductases
keywords: AOX; Debaryomyces hansenii; NAD(+) loss; NAD(+) transport; Physiological uncoupling; Respiratory complex I