Respiratory Chain Supercomplexes

Abstract

SummaryRespiratory chain supercomplexes have been isolated from mammalian and yeast mitochondria, and bacterial membranes. Functional roles of respiratory chain supercomplexes are catalytic enhancement, substrate channelling, and stabilization of complex I by complex III in mammalian cells. Bacterial supercomplexes are characterized by their relatively high detergent-stability compared to yeast or mammalian supercomplexes that are stable to sonication. The mobility of substrate cytochrome c increases in the order bacterial, yeast, and mammalian respiratory chain. In bacterial supercomplexes, the electron transfer between complexes III and IV involves movement of the mobile head of a tightly bound cytochrome c, whereas the yeast S. cerevisiae seems to use substrate channelling of a mobile cytochrome c, and mammalian respiratory chains have been described to use a cytochrome c pool. Dimeric ATP synthase seems to be speci c for mitochondrial OXPHOS systems. Monomeric complex V was found in Acetobacterium woodii and Paracoccus denitri cans.

Gluing the Respiratory Chain Together

“…The highly ordered state of these lipids necessary for their resolution supports a role for specific and tight association of defined lipid species with membrane proteins. Considerable evidence also supports the organization of the respiratory chain in both prokaryotes and eukaryotes into "respirasomes" or supercomplexes made up of smaller multimeric complexes (4). For oxidative phosphorylation, such supercomplexes may provide added efficiency by eliminating the need for diffusion of substrates and products between individual complexes and provide a means for channeling intermediates between individual complexes.…”

An Assembled Complex IV Maintains the Stability and Activity of Complex I in Mammalian Mitochondria

“…One favored model is that the respiratory complexes are embedded in the lipid bilayer of inner mitochondrial membrane and are connected electronically by diffusing ubiquinone and cytochrome c (2). However, with the recent development of blue native (BN) 4 -PAGE, a method for isolating intact membrane-bound protein complexes and thus particularly useful for investigating the integrity of mitochondrial respiratory complexes (3,4), supercomplexes that contain multiple respiratory complexes have been reported in bacteria (5), in yeast (6), and in mammalian (6) and plant mitochondria (7), suggesting an alternative model of direct channeling between complexes.…”

Steroidogenesis in MA-10 Mouse Leydig Cells Is Altered via Fatty Acid Import into the Mitochondria1

“…S1, available online at www.biolreprod.org). The initial analysis of the data generated from BN-PAGE was used to analyze the appearance of protein complexes I, III, and IV of the ETC, which were previously demonstrated to be associated under native conditions as a supercomplex [10,13]. We were able to identify protein complexes I, III, and IV migrating separately in protein complex form in the mitochondria from both control (Fig.…”

“…the electrons between complexes, resulting in the decrease of free radical formation with increasing ATP production [13,14]. These enzymatically active protein complexes have been identified and purified together via BN-PAGE where it has been demonstrated that ETC complexes can regulate their own stability in forming supercomplexes, responding to the energetic needs of the cell [10], Mitochondrial beta (b)-oxidation metabolizes long-chain fatty acids in the mitochondrial matrix, where it produces acetyl-CoA utilized in the citric acid cycle and donates reducing electrons to NADH and FADH 2 utilized by the ETC [15].…”