6FYC:
reference: Enzymatic control of dioxygen binding and functionalization of the flavin cofactor., Saleem-Batcha R, Stull F, Sanders JN, Moore BS, Palfey BA, Houk KN, Teufel R, Proc Natl Acad Sci U S A. 2018 Apr 23. pii: 1801189115. doi:, 10.1073/pnas.1801189115. PMID: 29686059

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