COX7A2L Is a Mitochondrial Complex III Binding Protein that Stabilizes the III2+IV Supercomplex without Affecting Respirasome Formation

Cell Rep. 2016 Aug 30;16(9):2387-98. doi: 10.1016/j.celrep.2016.07.081. Epub 2016 Aug 18.

Abstract

Mitochondrial respiratory chain (MRC) complexes I, III, and IV associate into a variety of supramolecular structures known as supercomplexes and respirasomes. While COX7A2L was originally described as a supercomplex-specific factor responsible for the dynamic association of complex IV into these structures to adapt MRC function to metabolic variations, this role has been disputed. Here, we further examine the functional significance of COX7A2L in the structural organization of the mammalian respiratory chain. As in the mouse, human COX7A2L binds primarily to free mitochondrial complex III and, to a minor extent, to complex IV to specifically promote the stabilization of the III2+IV supercomplex without affecting respirasome formation. Furthermore, COX7A2L does not affect the biogenesis, stabilization, and function of the individual oxidative phosphorylation complexes. These data show that independent regulatory mechanisms for the biogenesis and turnover of different MRC supercomplex structures co-exist.

MeSH terms

  • Animals
  • Electron Transport
  • Electron Transport Complex I / genetics
  • Electron Transport Complex I / metabolism*
  • Electron Transport Complex III / genetics
  • Electron Transport Complex III / metabolism*
  • Electron Transport Complex IV / genetics
  • Electron Transport Complex IV / metabolism*
  • Gene Expression
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Mice
  • Mitochondria, Heart / chemistry
  • Mitochondria, Heart / metabolism*
  • Mitochondrial Membranes / metabolism*
  • Myocardium / cytology
  • Myocardium / metabolism
  • Oxidative Phosphorylation*
  • Protein Binding
  • Protein Stability

Substances

  • Electron Transport Complex IV
  • Electron Transport Complex I
  • Electron Transport Complex III