5KJR:
reference: A Highly Conserved gp120 Inner Domain Residue Modulates Env Conformation and Trimer Stability., Ding S, Tolbert WD, Prevost J, Pacheco B, Coutu M, Debbeche O, Xiang SH, Pazgier M, Finzi A, J Virol. 2016 Jul 6. pii: JVI.01068-16. PMID: 27384653

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