1S6A:
reference: Crystallographic analysis of synechocystis cyanoglobin reveals the structural changes accompanying ligand binding in a hexacoordinate hemoglobin., Trent JT 3rd, Kundu S, Hoy JA, Hargrove MS, J Mol Biol 2004 Aug 20;341(4):1097-108. PMID: 15289104

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