Hypoxia-inducible gene domain 1 proteins in yeast mitochondria protect against proton leak through complex IV

Abstract

Hypoxia-inducible gene domain 1 (HIGD1) proteins are small integral membrane proteins, conserved from bacteria to humans, that associate with oxidative phosphorylation supercomplexes. Using yeast as a model organism, we have shown previously that its two HIGD1 proteins, Rcf1 and Rcf2, are required for the generation and maintenance of a normal membrane potential (ΔΨ) across the inner mitochondrial membrane (IMM). We postulated that the lower ΔΨ observed in the absence of the HIGD1 proteins may be due to decreased proton pumping by complex IV (CIV) or enhanced leak of protons across the IMM. Here we measured the ΔΨ generated by complex III (CIII) to discriminate between these possibilities. First, we found that the decreased ΔΨ observed in the absence of the HIGD1 proteins cannot be due to decreased proton pumping by CIV because CIII, operating alone, also exhibited a decreased ΔΨ when HIGD1 proteins were absent. Because CIII can neither lower its pumping stoichiometry nor transfer protons completely across the IMM, this result indicates that HIGD1 protein ablation enhances proton leak across the IMM. Second, we demonstrate that this proton leak occurs through CIV because ΔΨ generation by CIII is restored when CIV is removed from the cell. Third, the proton leak appeared to take place through an inactive population of CIV that accumulates when HIGD1 proteins are absent. We conclude that HIGD1 proteins in yeast prevent CIV inactivation, likely by preventing the loss of lipids bound within the Cox3 protein of CIV.

Angiotensin II type 1 receptor agonistic autoantibody blockade improves postpartum hypertension and cardiac mitochondrial function in rat model of preeclampsia

“…Uncontrolled complex IV activity was measured as the rate of oxygen consumption catalyzed by complex IV in broken, KCl-washed rat heart mitochondria as described previously [ 44 ] with some modifications. Electrons were provided to complex IV in 10 μg broken mitochondria by horse heart cytochrome c (20 μM), which was kept reduced by ascorbate (3 mM) and N , N , N ′, N ′-tetramethyl- p -phenylenediamine (TMPD; 0.3 mM).…”

Angiotensin II Type 1 Receptor Agonistic Autoantibody Blockade Improves Postpartum Hypertension and Cardiac Mitochondrial Function in Rat Model of Preeclampsia

“…Uncontrolled complex IV activity was measured as the rate of oxygen consumption catalyzed by complex IV in broken, KCl-washed rat heart mitochondria as described previously 44 with some modi cations. Renal Function.…”

Mining the Conserved Transcriptional Response to Phytophthora Infection for Factors Beyond the Known PR Genes

“…Besides the NDUFA4 family, there are also several other upregulated clusters populated with mitochondrial proteins. Among them is cluster #176, whose member proteins appear to be homologous to yeast respiratory chain supercomplex factor Rcf2, a hypoxia-inducible gene that also regulates cytochrome c oxidase (Rompler et al, 2016;Hoang et al, 2019). Several other clusters, such as USC #178, #285, #90 and #110, encode short mitochondrial proteins of unknown function, which might work in a similar pathway.…”