3MOO:
reference: Enzymatic ring-opening mechanism of verdoheme by the heme oxygenase: a combined X-ray crystallography and QM/MM study., Lai W, Chen H, Matsui T, Omori K, Unno M, Ikeda-Saito M, Shaik S, J Am Chem Soc. 2010 Sep 22;132(37):12960-70. PMID: 20806922

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