2APR:
reference: Structure and refinement at 1.8 A resolution of the aspartic proteinase from Rhizopus chinensis., Suguna K, Bott RR, Padlan EA, Subramanian E, Sheriff S, Cohen GH, Davies DR, J Mol Biol 1987 Aug 20;196(4):877-900. PMID: 3316666

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