4ZI9:
reference: Structure and Sequence Analyses of Clustered Protocadherins Reveal Antiparallel Interactions that Mediate Homophilic Specificity., Nicoludis JM, Lau SY, Scharfe CP, Marks DS, Weihofen WA, Gaudet R, Structure. 2015 Nov 3;23(11):2087-98. doi: 10.1016/j.str.2015.09.005. Epub 2015, Oct 15. PMID: 26481813

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