Modulation of the Respiratory Supercomplexes in Yeast: ENHANCED FORMATION OF CYTOCHROME OXIDASE INCREASES THE STABILITY AND ABUNDANCE OF RESPIRATORY SUPERCOMPLEXES

Vincenzo Zara,Annalea Conte,Tie-Zhong Cui,Jennifer L Fox,Dennis R Winge

doi:10.1074/jbc.m113.523688

Vincenzo Zara, Annalea Conte + Show 3 more

Open Access

https://doi.org/10.1074/jbc.m113.523688

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Abstract

Yeast cells deficient in the Rieske iron-sulfur subunit (Rip1) of ubiquinol-cytochrome c reductase (bc1) accumulate a late core assembly intermediate, which weakly associates with cytochrome oxidase (CcO) in a respiratory supercomplex. Expression of the N-terminal half of Rip1, which lacks the C-terminal FeS-containing globular domain (designated N-Rip1), results in a marked stabilization of trimeric and tetrameric bc1-CcO supercomplexes. Another bc1 mutant (qcr9Δ) stalled at the same assembly intermediate is likewise converted to stable supercomplex species by the expression of N-Rip1, but not by expression of intact Rip1. The N-Rip1-induced stabilization of bc1-CcO supercomplexes is independent of the Bcs1 translocase, which mediates Rip1 translocation during bc1 biogenesis. N-Rip1 induces the stabilization of bc1-CcO supercomplexes through an enhanced formation of CcO. The association of N-Rip1 with the late core bc1 assembly intermediate appears to confer stabilization of a CcO assembly intermediate. This induced stabilization of CcO is dependent on the Rcf1 supercomplex stabilization factor and only partially dependent on the presence of cardiolipin. N-Rip1 exerts a related induction of CcO stabilization in WT yeast, resulting in enhanced respiration. Additionally, the impact of CcO stabilization on supercomplexes was observed by means other than expression of N-Rip1 (via overexpression of CcO subunits Cox4 and Cox5a), demonstrating that this is a general phenomenon. This study presents the first evidence showing that supercomplexes can be stabilized by the stimulated formation of CcO.

Highlights

The cytochrome bc1 complex weakly associates with cytochrome oxidase (CcO) in the absence of the Rieske Rip1 subunit
We demonstrated previously that expression of just the N-terminal domain of Rip1 in rip1⌬ BY4741 yeast cells induced stabilization of electron transfer chain (ETC) supercomplexes without the Rip1 truncate being stably associated with the supercomplexes [28]
In the absence of Rip1, CcO largely fractionated in a monomeric complex after blue native PAGE (BN-PAGE), low abundance supercomplexes can be seen in digitonin-solubilized mitochondrial lysates in Fig. 1B

Summary

Introduction

The cytochrome bc complex weakly associates with cytochrome oxidase (CcO) in the absence of the Rieske Rip subunit. Yeast cells deficient in the Rieske iron-sulfur subunit (Rip1) of ubiquinol-cytochrome c reductase (bc1) accumulate a late core assembly intermediate, which weakly associates with cytochrome oxidase (CcO) in a respiratory supercomplex. Expression of the N-terminal half of Rip, which lacks the C-terminal FeS-containing globular domain (designated N-Rip1), results in a marked stabilization of trimeric and tetrameric bc1-CcO supercomplexes. Another bc mutant (qcr9⌬) stalled at the same assembly intermediate is likewise converted to stable supercomplex species by the expression of N-Rip, but not by expression of intact Rip.

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