5XF8:
reference: Open-ringed structure of the Cdt1-Mcm2-7 complex as a precursor of the MCM double hexamer., Zhai Y, Cheng E, Wu H, Li N, Yung PY, Gao N, Tye BK, Nat Struct Mol Biol. 2017 Mar;24(3):300-308. doi: 10.1038/nsmb.3374. Epub 2017, Feb 13. PMID: 28191894

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