1LVU:
reference: Crystal structure of calf spleen purine nucleoside phosphorylase with two full trimers in the asymmetric unit: important implications for the mechanism of catalysis., Bzowska A, Koellner G, Wielgus-Kutrowska B, Stroh A, Raszewski G, Holy A, Steiner T, Frank J, J Mol Biol 2004 Sep 17;342(3):1015-32. PMID: 15342253

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