1BP4:
reference: Use of papain as a model for the structure-based design of cathepsin K inhibitors: crystal structures of two papain-inhibitor complexes demonstrate binding to S'-subsites., LaLonde JM, Zhao B, Smith WW, Janson CA, DesJarlais RL, Tomaszek TA, Carr TJ, Thompson SK, Oh HJ, Yamashita DS, Veber DF, Abdel-Meguid SS, J Med Chem 1998 Nov 5;41(23):4567-76. PMID: 9804696

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