The absence of the mitochondrial ATP synthase delta subunit promotes a slow growth phenotype of rho(-) yeast cells by a lack of assembly of the catalytic sector F-1

In the yeast Saccharomyces cerevisiae, inactivation of the gene encoding the delta subunit of the ATP synthase led to a lack of assembly of the catalytic sector. In addition a slow-growth phenotype was observed on fermentable medium. This alteration appears in strains lacking intact mitochondrial DNA and showing a defect in the assembly of the catalytic sector, such as the yeast strain inactivated in the gene encoding the epsilon subunit. In rho(-) mitochondria having an intact F-1, the ion movement resulting from the exchange of ADP formed in the organelle and ATP entering the mitochondrial compartment led to a mitochondrial transmembranous potential Delta Psi that was sensitive to carboxyactractyloside. This ion movement was dramatically decreased in rho(-) mitochondria lacking the delta subunit and thus the F-1 sector, whereas a cell devoid of delta subunit and complemented with a plasmid harboring the ATP delta gene displayed an assembled F-1, a normal generation time and a fully restored mitochondrial potential. This result could be linked to the involvement of the membrane potential Delta Psi which is indispensible for mitochondrial biogenesis.