Table 2. Distribution, Location, and Quaternary Structure of SODs and SORs.
| Archaea | Bacteria | Eukarya | ||||
|---|---|---|---|---|---|---|
| NiSOD | none | cytosol (hexamer) | cytosola (unknown) | |||
| FeSOD | cytosol (tetramer) | cytosol (dimer or tetramer) | cytosol, glycosomes, mitochondriab (tetramerb) | |||
| chloroplasts (dimer or tetramer) | ||||||
| MnSOD | cytosol (tetramer) | cytosol (dimer or tetramer) | mitochondrial matrix (tetramer) | |||
| cytosolc (dimer) | ||||||
| peroxisomes (tetramer) | ||||||
| chloroplasts (unknown) | ||||||
| CuZnSOD | genes identified in Methanobacteriad | periplasm (monomer or dimer) | cytosolc (dimer) | |||
| mitochondrial IMS, nucleus (dimer) | ||||||
| chloroplasts, peroxisomes (dimer) | ||||||
| extracellular spacee (tetramer) | ||||||
| SOR | cytosolf (tetramer or dimerg) | cytosolf (tetramer or dimerg) | unknown (tetramer) | |||
Eukaryotic NiSOD is found in the cytosol of some green algae.
FeSOD is found in protist Tetrahymena pyriformis.
Cytosolic MnSOD is found in C. albicans and many crustaceans, which also express a mitochondrial MnSOD.
The gene of CuZnSOD has been identified in two Methanobacteria, Methanosarcina acetivorans (Gene Access Number: NP_617328.1) and Methanocella arvoryzae (Gene Access Number: YP_684494.1).
Extracellular CuZnSOD is found in mammals and many plants.
The proposed cytosolic location of prokaryotic SORs comes from the absence of detectable translocation signal peptides in the translated amino acid sequences; there are, however (see section 7), a few sequences with putative twin-arginine signatures.
1Fe-SORs with a single catalytic domain are tetramers; SORs with an extra desulforedoxin-like domain, with or without the FeCys4 metal center, are homodimers.