2CN4:
reference: The crystal structure of the secreted dimeric form of the hemophore HasA reveals a domain swapping with an exchanged heme ligand., Czjzek M, Letoffe S, Wandersman C, Delepierre M, Lecroisey A, Izadi-Pruneyre N, J Mol Biol. 2007 Jan 26;365(4):1176-86. Epub 2006 Oct 25. PMID: 17113104

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