Yeast Cells Depleted in Atp14p Fail to Assemble Atp6p within the ATP Synthase and Exhibit Altered Mitochondrial Cristae Morphology

Vanessa Goyon,Rémi Fronzes,Bénédicte Salin,Jean-Paul Di-Rago,Jean Velours,Daniel Brèthes

doi:10.1074/jbc.m800204200

Abstract

Within the yeast mitochondrial ATP synthase, subunit h is a small nuclear encoded protein belonging to the so-called "peripheral stalk" that connects the enzyme catalytic F(1) component to the mitochondrial inner membrane. This study examines the role of subunit h in ATP synthase function and assembly using a regulatable, doxycycline-repressible subunit h gene to overcome the strong instability of the mtDNA previously observed in strains lacking the native subunit h gene. Yeast cells expressing less than 3% of subunit h, but still containing intact mitochondrial genomes, grew poorly on respiratory substrates because of a major impairment of ATP synthesis originating from the ATP synthase, whereas the respiratory chain complexes were not affected. The lack of ATP synthesis in the subunit h-depleted (deltah) mitochondria was attributed to defects in the assembly/stability of the ATP synthase. A main feature of deltah-mitochondria was a very low content (<6%) in the mitochondrially encoded Atp6p subunit, an essential component of the enzyme proton channel, which was in large part because of a slowing down in translation. Interestingly, depletion of subunit h resulted in dramatic changes in mitochondrial cristae morphology, which further supports the existence of a link between the ATP synthase and the folding/biogenesis of the inner mitochondrial membrane.

Highlights

The ATP synthase complex can be described as a molecular rotary motor
The absence of subunit e and/or subunit g results in a strong alteration of the cristae morphology [8], indicating that the ATP synthase controls in some way the biogenesis of the inner mitochondrial membrane
Subunit h-depleted Mitochondrial ATP Synthase to be functionally equivalent as evidenced by the ability of F6 to complement the absence of subunit h gene in ⌬atp14 yeast cells [19]

Summary

Introduction

The ATP synthase complex can be described as a molecular rotary motor. The rotor, which is driven by the proton flux through the inner membrane, is composed of the subunit 9 oligomer (10 copies) and the central stalk subunits ␥, ␦, and ⑀. The absence of subunit e and/or subunit g results in a strong alteration of the cristae morphology [8], indicating that the ATP synthase controls in some way the biogenesis of the inner mitochondrial membrane. Depletion of Subunit h Severely Compromises the Respiratory Growth of Yeast—We have constructed the RFY5-1 strain by transformation of yeast cells with a plasmid where the coding sequence of ATP14 is under the control of a doxycycline-repressible promoter followed by deletion of the chromosomal ATP14 gene.

Results

Conclusion