Heme O (or haem O) differs from the closely related
heme A by having a
methyl group at ring position 8 instead of the
formyl group. The
isoprenoid chain at position 2 is the same.
Heme O, found in the bacterium Escherichia coli,[1] functions in a similar manner to heme A in mammalian oxygen reduction.
^Myles R. Cheesman; Vasily S. Oganesyan; Nicholas J. Watmough; Clive S. Butler; Andrew J. Thomson (2004). "The Nature of the Exchange Coupling between High-Spin Fe(III) Heme o3 and CuB(II) in Escherichia coli Quinol Oxidase, Cytochrome bo3: MCD and EPR Studies". J. Am. Chem. Soc. 126 (13): 4157–4166.
doi:
10.1021/ja038858m.
PMID15053605.