The most common supercomplexes observed are Complex I/III, Complex I/III/IV, and Complex III/IV. Most of Complex II is found in a free-floating form in both plant and animal mitochondria. Complex V can be found co-migrating as a dimer with other supercomplexes, but scarcely as part of the supercomplex unit.
Supercomplex assembly appears to be dynamic and respiratory enzymes are able to alternate between participating in large respirasomes and existing in a free state. It is not known what triggers changes in complex assembly, but research has revealed that the formation of supercomplexes is heavily dependent upon the lipid composition of the mitochondrial membrane, and in particular requires the presence of cardiolipin, a unique mitochondrial lipid. In yeast mitochondria lacking cardiolipin, the number of enzymes forming respiratory supercomplexes was significantly reduced. According to Wenz et al. (2009), cardiolipin stabilizes the supercomplex formation by neutralizing the charges of lysine residues in the interaction domain of Complex III with Complex IV. In 2012, Bazan et al. was able to reconstitute trimer and tetramer Complex III/IV supercomplexes from purified complexes isolated from Saccharomyces cerevisiae and exogenous cardiolipin liposomes.
Another hypothesis for respirasome formation is that membrane potential may initiate changes in the electrostatic/hydrophobic interactions mediating the assembly/disassembly of supercomplexes.