1Y1U:
reference: Structure of the unphosphorylated STAT5a dimer., Neculai D, Neculai AM, Verrier S, Straub K, Klumpp K, Pfitzner E, Becker S, J Biol Chem. 2005 Dec 9;280(49):40782-7. Epub 2005 Sep 28. PMID: 16192273

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