4JVW:
reference: High-resolution structures of the IgM Fc domains reveal principles of its hexamer formation., Muller R, Grawert MA, Kern T, Madl T, Peschek J, Sattler M, Groll M, Buchner J, Proc Natl Acad Sci U S A. 2013 Jun 18;110(25):10183-8. doi:, 10.1073/pnas.1300547110. Epub 2013 Jun 3. PMID: 23733956

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