1XD9:
reference: Structural and biochemical implications of single amino acid substitutions in the nucleotide-dependent switch regions of the nitrogenase Fe protein from Azotobacter vinelandii., Jang SB, Jeong MS, Seefeldt LC, Peters JW, J Biol Inorg Chem 2004 Dec;9(8):1028-33. Epub 2004 Nov 10. PMID: 15549494

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