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. Author manuscript; available in PMC: 2013 Feb 25.
Published in final edited form as: J Mol Biol. 2010 Jun 25;401(3):350–362. doi: 10.1016/j.jmb.2010.06.041

Fig. 8.

Fig. 8

Proposed Michael addition (nucleophilic) reaction mechanism for covalent adduct formation at CcmE His130. The imidazole group of the CcmE His130 is indicated and is attached to the β-carbon of the heme 2-vinyl. Full arrows represent two electron transfers. The oxidation state of the heme is shown for each step. Mechanism of initial oxidation of heme (Fe2+ to Fe3+) is unknown. UQ, ubiquinone; MQ, menaquinone; FAD, flavin adenine dinucleotide; NAD, nicotinamide dinucleotide (figure is modified from Kranz et al.10).