Abstract
Cox23 is a known conserved assembly factor for cytochrome c oxidase, although its role in cytochrome c oxidase (CcO) biogenesis remains unresolved. To gain additional insights into its role, we isolated spontaneous suppressors of the respiratory growth defect in cox23∆ yeast cells. We recovered independent colonies that propagated on glycerol/lactate medium for cox23∆ cells at 37°C. We mapped these mutations to the mitochondrial genome and specifically to COX1 yielding an I101F substitution. The I101F Cox1 allele is a gain-of-function mutation enabling yeast to respire in the absence of Cox23. CcO subunit steady-state levels were restored with the I101F Cox1 suppressor mutation and oxygen consumption and CcO activity were likewise restored. Cells harboring the mitochondrial genome encoding I101F Cox1 were used to delete genes for other CcO assembly factors to test the specificity of the Cox1 mutation as a suppressor of cox23∆ cells. The Cox1 mutant allele fails to support respiratory growth in yeast lacking Cox17, Cox19, Coa1, Coa2, Cox14 or Shy1, demonstrating its specific suppressor activity for cox23∆ cells.
Highlights
Cytochrome c oxidase (CcO) of the mitochondrial respiratory chain couples the reduction of molecular oxygen with proton translocation across the inner membrane (IM) to generate the membrane potential used to synthesize ATP
We describe the isolation of a robust suppressor of the respiratory defect in cox23∆ cells that mapped to the mitochondrial-encoded complexes [5-8]. Subunit 1 (Cox1) subunit
The growth impairment was sufficiently strong in BY4741 and BY4743 cells cultured at 37°C
Summary
Cytochrome c oxidase (CcO) of the mitochondrial respiratory chain couples the reduction of molecular oxygen with proton translocation across the inner membrane (IM) to generate the membrane potential used to synthesize ATP. In the absence of any clear functional data on Cox23, we screened for spontaneous suppressors of the respiratory defect of cox23∆ cells. We describe the isolation of a robust suppressor of the respiratory defect in cox23∆ cells that mapped to the mitochondrial-encoded Cox1 subunit. Cox1 suppressor of cox23 mutant ent but reduced relative to WT cells (Fig. 1C).
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