Oxidative phosphorylation supercomplexes and respirasome reconstitution of the colorless alga Polytomella sp

Abstract

The proposal that the respiratory complexes can associate with each other in larger structures named supercomplexes (SC) is generally accepted. In the last decades most of the data about this association came from studies in yeasts, mammals and plants, and information is scarce in other lineages. Here we studied the supramolecular association of the F₁F_O-ATP synthase (complex V) and the respiratory complexes I, III and IV of the colorless alga Polytomella sp. with an approach that involves solubilization using mild detergents, n-dodecyl-β-D-maltoside (DDM) or digitonin, followed by separation of native protein complexes by electrophoresis (BN-PAGE), after which we identified oligomeric forms of complex V (mainly V₂ and V₄) and different respiratory supercomplexes (I/IV₆, I/III₄, I/IV). In addition, purification/reconstitution of the supercomplexes by anion exchange chromatography was also performed. The data show that these complexes have the ability to strongly associate with each other and form DDM-stable macromolecular structures. The stable V₄ ATPase oligomer was observed by electron-microscopy and the association of the respiratory complexes in the so-called "respirasome" was able to perform in-vitro oxygen consumption.

Keywords: Chlorophycean algae; F(1)F(O) ATP synthase; Mitochondrial supercomplexes; Oligomeric complex V; Oxidative phosphorylation; Respirasome.