| Complex | Name | Molecular Weight * | Alternative Name | Protein Number † | Gene Number ‡ |
| I | NADH–ubiquinone oxidoreductase | 39,000-dalton subunit | 42.5 | α subcomplex, 9 | Q16795 | NDUFA9 |
| 30,000-dalton subunit | 30.2 | iron–sulfur protein 3 | O75489 | NDUFS3 |
| 20,000-dalton subunit | 20.0 | ND6 protein (NDU subunit 6) | P03923 | MTND6 |
| 17,000-dalton subunit | 15.5 | β subcomplex, 6 | O95139 | NDUFB6 |
| 15,000-dalton subunit | 15.1 | α subcomplex, 6 | P56556 | NDUFA6 |
| II | Succinate–ubiquinone oxidoreductase | 70,000-dalton subunit | 72.7 | flavoprotein | P31040 | SDHA |
| 30,000-dalton subunit | 31.6 | iron–sulfur protein | P21912 | SDHB |
| III | Ubiquinone–cytochrome c oxidoreductase | Core 1 subunit | 51.6 | none | P31930 | UQCRC1 |
| Core 2 subunit | 48.5 | none | P22695 | UQCRC2 |
| Iron–sulfur subunit | 29.6 | Rieske iron–sulfur protein | P47985 | UQCRFS1 |
| 10,000-dalton subunit | 9.6 § | subunit VII | P13271 § | UCRQ |
| IV | Cytochrome c oxidase (COX) | Subunit I | 57.0 | COX I | P00395 | MTCO1 |
| Subunit II | 25.6 | COX II | P00403 | MTCO2 |
| Subunit III | 29.9 | COX III | P00414 | MTCO3 |
| Subunit IV | 19.6 | COX IV | P13073 | COX4 |
| Subunit Va | 16.8 | COX Va | P20674 | COX5A |
| Subunit Vb | 13.7 | COX Vb | P10606 | COX5B |
| Subunit VIa-L ** | 9.5 § | COX VIa | P13182 § | COX6A1 |
| Subunit VIb | 10.0 § | COX VIb | P00429 § | COX6B |
| Subunit VIc | 8.8 | COX VIc | P09669 | COX6C |
| Subunit VIIa-H/L ** | 9.4 | COX VIIa | P14406 | COX7A2 |
| Subunit VIIb | 9.2 | COX VIIb | P24311 | COX7B |
| V | ATP synthase | α subunit | 59.8 | F1 complex, α subunit | P25705 | ATP5A1 |
| β subunit | 56.6 | F1 complex, β subunit | P06576 | ATP5B |
| d subunit | 18.4 | none | O75947 | ATP5H |
| OSCP subunit †† | 23.2 | F1 complex, O subunit | P48047 | ATP5O |
| Inhibitor protein (IP) | 12.3 § | IF1 | P01096 § | ATPI |
| * Molecular weight in kilodaltons. † Protein reference numbers are from SWISS-PROT, an annotated protein sequence database (http://www.ebi.ac.uk/swissprot/) and refer to the human sequence, unless otherwise noted. ‡ Gene reference numbers are from Genbank, which can be accessed through Entrez (http://www3.ncbi.nlm.nih.gov/Entrez/). § Protein number and molecular weight are for the bovine sequence. **[ H = heart-specific isotope; L = liver-specific isotope. †† OSCP = oligomycin sensitivity–conferring protein. |