4GTF:
reference: Folate binding site of flavin-dependent thymidylate synthase., Koehn EM, Perissinotti LL, Moghram S, Prabhakar A, Lesley SA, Mathews II, Kohen A, Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15722-7. Epub 2012 Sep 10. PMID: 23019356

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