3K9A:
reference: Structural characterization of HIV gp41 with the membrane-proximal external region., Shi W, Bohon J, Han DP, Habte H, Qin Y, Cho MW, Chance MR, J Biol Chem. 2010 Jul 30;285(31):24290-8. Epub 2010 Jun 4. PMID: 20525690

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