Classes
In 1991 R. P. Ambler recognized four classes of cytochrome c:
- Class I includes the lowspin soluble cytochrome c of mitochondria and bacteria. It has the heme-attachment site towards the N terminus of histidine and the sixth ligand provided by a methionine residue towards the C terminus.
- Class II includes the highspin cytochrome c'. It has the heme-attachment site closed to the N terminus of histidine.
- Class III comprises the low redox potential multiple heme cytochromes. The heme c groups are structurally and functionally nonequivalent and present different redox potentials in the range 0 to -400 mV.
- Class IV was originally created to hold the complex proteins that have other prosthetic groups as well as heme c.
Read more about this topic: Cytochrome C
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