Inactivation of the gene encoding the 11‐kDa subunit VIII of the ubiquinol–cytochrome‐c oxidoreductase in Saccharomyces cerevisiae

Abstract

The single nuclear gene encoding the 11‐kDa subunit VIII of the ubiquinol– cytochrome‐c oxidoreductase (complex III) in Saccharomyces cerevisiae has been inactivated by a one‐step gene disruption procedure. Inactivation results in a loss of ubiquinol–cytochrome‐c oxidoreductase activity (< 1 % wild type) and respiratory deficiency. Cells lacking the 11‐kDa protein also display lowered steady‐state levels of other complex‐III subunits encoded by nuclear genes including the 14‐kDa subunit VII and the Rieske Fe‐S protein and of the mitochondrially encoded cytochrome b. The steady‐state levels of the transcripts from the genes encoding these proteins are however not reduced. The results strongly imply that the 11‐kDa protein plays an important role in regulating the synthesis of complex III at the post‐transcriptional level, most likely assembly. Separation of chromosomes by pulsed‐field gel electrophoresis of DNA of wild‐type and of the mutant lacking the 11‐kDa‐protein gene followed by Southern blot analysis reveals that the latter gene is located on chromosome X rather than on XII as reported by Van Loon et al. [Mol. Gen. Genet. 197 (1984) 219–241]. Copyright © 1988, Wiley Blackwell. All rights reserved