4GVS:
reference: Structure and Catalytic Mechanism of N(5),N(10)-Methenyl-tetrahydromethanopterin Cyclohydrolase., Upadhyay V, Demmer U, Warkentin E, Moll J, Shima S, Ermler U, Biochemistry. 2012 Oct 23;51(42):8435-43. doi: 10.1021/bi300777k. Epub 2012 Oct, 8. PMID: 23013430

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