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. Author manuscript; available in PMC: 2009 Dec 1.
Published in final edited form as: Nat Prod Rep. 2008 Sep 9;25(6):1118–1130. doi: 10.1039/b717196j

Figure 1.

Figure 1

Chemical structures of (A) heme b, (B) heme c, and (C) heme d1. The Fisher numbering system for heme substituents is shown in (A). The curve in (B) represents a peptide segment; usually two residues separate the two Cys, and the His axial ligand follows the Cys attached to position 4. Heme o has a hydroxyfarnesyl group in place of vinyl 2 in (A), and heme a has a hydroxyfarnesyl group in place of vinyl 2 and a formyl group in place of methyl 8.