6HSD:
reference: The Crystal Structure of the Transcription Regulator RsrR Reveals a [2Fe-2S] Cluster Coordinated by Cys, Glu and His Residues., Volbeda A, Pellicer Martinez MT, Crack JC, Amara P, Gigarel O, Munnoch JT, Hutchings MI, Darnault C, Le Brun NE, Fontecilla-Camps JC, J Am Chem Soc. 2019 Jan 18. doi: 10.1021/jacs.8b10823. PMID: 30657661

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