Updated project metadata. Mitochondrial respiratory chain (MRC) complexes I, III and IV are associated into large molecular structures named supercomplexes (SCs) or respirasomes, whose functional roles remain to be fully understood. Biochemical analyses in a diversity of OXPHOS-deficient cellular and animal models support the idea that one of the SCs function is to confer stability to individual MRC complexes, in particular to complex I (CI). To gain insight into the mechanisms that regulate the structural interdependences among MRC complexes, we performed complexome profiling of human cybrids laking mitochondrial genes Cox1 or Cox2 and compared protein assemblies and intermediates to control 143B cells.