2BN5:
reference: Structural basis of the interaction between P-element somatic inhibitor and U1-70k essential for the alternative splicing of P-element transposase., Ignjatovic T, Yang JC, Butler J, Neuhaus D, Nagai K, J Mol Biol. 2005 Aug 5;351(1):52-65. PMID: 15990112

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