3LX4:
reference: Stepwise [FeFe]-hydrogenase H-cluster assembly revealed in the structure of HydA(DeltaEFG)., Mulder DW, Boyd ES, Sarma R, Lange RK, Endrizzi JA, Broderick JB, Peters JW, Nature. 2010 May 13;465(7295):248-51. Epub 2010 Apr 25. PMID: 20418861

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