4URH:
reference: Crystallographic studies of [NiFe]-hydrogenase mutants: towards consensus structures for the elusive unready oxidized states., Volbeda A, Martin L, Barbier E, Gutierrez-Sanz O, De Lacey AL, Liebgott PP, Dementin S, Rousset M, Fontecilla-Camps JC, J Biol Inorg Chem. 2014 Oct 15. PMID: 25315838

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