4VHB:
reference: Anticooperative ligand binding properties of recombinant ferric Vitreoscilla homodimeric hemoglobin: a thermodynamic, kinetic and X-ray crystallographic study., Bolognesi M, Boffi A, Coletta M, Mozzarelli A, Pesce A, Tarricone C, Ascenzi P, J Mol Biol 1999 Aug 20;291(3):637-50. PMID: 10448042

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