4Y8S:
reference: Systematic Analyses of Substrate Preferences of 20S Proteasomes Using Peptidic Epoxyketone Inhibitors., Huber EM, de Bruin G, Heinemeyer W, Paniagua Soriano G, Overkleeft HS, Groll M, J Am Chem Soc. 2015 Jun 11. PMID: 26020686

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