title: Proton pumping complex I increases growth yield in Candida utilis.
abstract: In living cells, growth is the result of coupling between substrate catabolism and multiple metabolic processes that take place during net biomass formation and cellular maintenance processes. A crucial parameter for growth evaluation is its yield, i.e. the efficiency of the transformation processes. The yeast Candida utilis is of peculiar interest since its mitochondria exhibit a complex I that is proposed to pump protons but also an external NADH dehydrogenase that do not pump protons. Here, we show that in C. utilis cells grown on non-fermentable media, growth yield is 30% higher as compared to that of Saccharomyces cerevisiae that do not exhibit a complex I. Moreover, ADP/O determination in C. utilis shows that electrons coming from internal NADH dehydrogenase go through proton pumping complex I, whereas electrons coming from external NADH dehydrogenases do not go through proton pumping complex I. Furthermore, we show that electron competition strictly depends on extra-mitochondrial NADH concentration, i.e. the higher the extra-mitochondrial NADH concentration, the higher the competition process with a right way for electrons coming from external NADH dehydrogenases. Such a complex regulation in C. utilis allows an increase in growth yield when cytosolic NADH is not plentiful but still favors the cytosolic NADH re-oxidation at high NADH, favoring biomass generation metabolic pathways.
authors.affiliation: Institute of Biochemistry and Genetics of the Cell, CNRS UMR 5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France; Université de Bordeaux, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France.
authors.forename: Nicole
authors.initials: N
authors.lastname: Avéret
authors.affiliation: Institute of Biochemistry and Genetics of the Cell, CNRS UMR 5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France; Université de Bordeaux, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France.
authors.forename: Marie-Lise
authors.initials: ML
authors.lastname: Jobin
authors.affiliation: Institute of Biochemistry and Genetics of the Cell, CNRS UMR 5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France; Université de Bordeaux, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France.
authors.forename: Anne
authors.initials: A
authors.lastname: Devin
authors.affiliation: Institute of Biochemistry and Genetics of the Cell, CNRS UMR 5095, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France; Université de Bordeaux, 1 Rue Camille Saint-Saëns, 33077 Bordeaux Cedex, France. Electronic address: michel.rigoulet@ibgc.cnrs.fr.
authors.forename: Michel
authors.initials: M
authors.lastname: Rigoulet
keywords: Candida utilis; Growth yield; Mitochondria; Oxidative phosphorylation; Saccharomyces cerevisiae; Yeast