PROPERTIES OF YEAST-CELLS DEPLETED OF THE OSCP SUBUNIT OF MITOCHONDRIAL ATP SYNTHASE BY REGULATED EXPRESSION OF THE ATP5 GENE

OSCP is a subunit of the F-A stalk sector of yeast mitochondrial ATP s ynthase complex. Cells of a null mutant for OSCP, constructed by disru ption of the chromosomal ATP5 gene of Saccharomyces cerevisiae, exhibi ted a high level of genetic instability (petite formation). Study of t he effects of ablation of OSCP required the development of a progressi ve depletion strategy. Introduction of a vector bearing an ATP5 gene c assette under GAL1 transcriptional control into null mutant cells gave rise to a stable yeast strain from which OSCP could be depleted in a controlled manner by manipulation of the level of galactose in the gro wth medium. Cells progressively depleted of OSCP exhibited properties of cellular respiration indicative of a decline in the functional coup ling of the catalytic F-1 sector to the proton channel F-0 sector (nor mally linked by F-A). Cells depleted of OSCP also exhibited a physical uncoupling of F-1 from other subunits of the complex such that other F-A subunits and F-0 subunit 6 were not recovered in immunoprecipitate s of ATP synthase complexes. Thus, OSCP plays a role in the assembly a s well as function of the enzyme complex.