Figure 2. Respiratory complexes and SCs composition.

(a) Respiratory super-complexes are formed by different composition of complexes. Key factors are the expression of different subunit isoforms important for CIV dimerization (COX7A2, COX7A1, COX6A1, COX6A2), the assembly factors SCAF1 (important for CIII and IV interaction) and MCJ (inhibitor of CI and CIII assembly), MIM lipid composition (CL: cardiolipin, PE: phosphatidylethanolamine, PG: plasmalogen). (b) Respirasome alternative ternary interactions. N-respirasome may include a single copy of CIV2 instead of CIV. Moreover, the stoichiometry of megacomplex (2I + III₂ + 2IV) is represented. The following pdb structures were used to develop this figure: CI (5xtd, Homo sapiens), CIII2 (5xte, Homo sapiens), CIV (5z62, Homo sapiens), CIV2 (1occ, Bos taurus), Loose N-respirasome (5j7y, Ovis aries), Tight N-respirasome (5j4z, Ovis aries) and Megacomplex (Homo sapiens, Bos taurus). c) BN-PAGE of 2 h [³⁵S]-methionine pulse labeled mtDNA encoded proteins wild-type mouse embryonic fibroblasts from and harvested after 24 h of chase.