2FIV:
reference: Crystal structures of the inactive D30N mutant of feline immunodeficiency virus protease complexed with a substrate and an inhibitor., Laco GS, Schalk-Hihi C, Lubkowski J, Morris G, Zdanov A, Olson A, Elder JH, Wlodawer A, Gustchina A, Biochemistry. 1997 Sep 2;36(35):10696-708. PMID: 9271500

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