1RQF:
reference: Structure of the regulatory subunit of CK2 in the presence of a p21(WAF1) peptide demonstrates flexibility of the acidic loop., Bertrand L, Sayed MF, Pei XY, Parisini E, Dhanaraj V, Bolanos-Garcia VM, Allende JE, Blundell TL, Acta Crystallogr D Biol Crystallogr 2004 Oct;60(Pt 10):1698-704. Epub 2004, Sep 23. PMID: 15388915

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