1MG1:
reference: Crystal structure of human T cell leukemia virus type 1 gp21 ectodomain crystallized as a maltose-binding protein chimera reveals structural evolution of retroviral transmembrane proteins., Kobe B, Center RJ, Kemp BE, Poumbourios P, Proc Natl Acad Sci U S A 1999 Apr 13;96(8):4319-24. PMID: 10200260

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