| Component in human (yeast/bacteria) | Function |
|---|---|
| SDHA (Sdh1/SdhA) | Component of CII; part of the matrix portion of CII, contains the SDH catalytic site containing FAD;~70 kDa |
| SDHB (Sdh2/SdhB) | Component of CII; part of the matrix portion of CII, contains three [Fe–S] clusters, carries electrons from the catalytic site in SDHA to the UbQ site;~30 kDa |
| SDHC (Sdh3/SdhC) | Component of CII, buried in the IMM, contributes to the UbQ site;~18 kDa; proposed to play a noncanonical role in the formation of the translocator of the inner membrane complex |
| SDHD (Sdh4/SdhD) | Component of CII; buried in the IMM, contributes to the UbQ site;~12 kDa |
| SDHAF1 (Sdh6/nsa) | Assembly factor 1; involved in [Fe–S] insertion into SDHB |
| SDHAF2 or SDH5 (Sdh5/SdhE) | Assembly factor 2; also known as SDH5; shown to insert FAD into SDHA; recent data indicate its redundancy, at least in some types of mammalian cells |
| SDHAF3 (Sdh7 or Acn9/ns) | Assembly factor 3; thought to be involved in [Fe–S] insertion into SDHB |
| SDHAF4 (Sdh8/ns) | Assembly factor 5; proposed to facilitate interaction of SDHA and SDHB (demonstrated for their Sdha and Sdh2 Drosophila homologs) |
a
ns, not studied/uncharacterized