1F1V:
reference: Crystallographic comparison of manganese- and iron-dependent homoprotocatechuate 2,3-dioxygenases., Vetting MW, Wackett LP, Que L Jr, Lipscomb JD, Ohlendorf DH, J Bacteriol 2004 Apr;186(7):1945-58. PMID: 15028678

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