Crystal structure, conformational fixation and entry-related interactions of mature ligand-free HIV-1 Env.
Do Kwon, Y., Pancera, M., Acharya, P., Georgiev, I.S., Crooks, E.T., Gorman, J., Joyce, M.G., Guttman, M., Ma, X., Narpala, S., Soto, C., Terry, D.S., Yang, Y., Zhou, T., Ahlsen, G., Bailer, R.T., Chambers, M., Chuang, G.Y., Doria-Rose, N.A., Druz, A., Hallen, M.A., Harned, A., Kirys, T., Louder, M.K., O'Dell, S., Ofek, G., Osawa, K., Prabhakaran, M., Sastry, M., Stewart-Jones, G.B., Stuckey, J., Thomas, P.V., Tittley, T., Williams, C., Zhang, B., Zhao, H., Zhou, Z., Donald, B.R., Lee, L.K., Zolla-Pazner, S., Baxa, U., Schon, A., Freire, E., Shapiro, L., Lee, K.K., Arthos, J., Munro, J.B., Blanchard, S.C., Mothes, W., Binley, J.M., McDermott, A.B., Mascola, J.R., Kwong, P.D.(2015) Nat Struct Mol Biol 22: 522-531
- PubMed: 26098315 
- DOI: https://doi.org/10.1038/nsmb.3051
- Primary Citation of Related Structures:  
4ZMJ - PubMed Abstract: 
As the sole viral antigen on the HIV-1-virion surface, trimeric Env is a focus of vaccine efforts. Here we present the structure of the ligand-free HIV-1-Env trimer, fix its conformation and determine its receptor interactions. Epitope analyses revealed trimeric ligand-free Env to be structurally compatible with broadly neutralizing antibodies but not poorly neutralizing ones. We coupled these compatibility considerations with binding antigenicity to engineer conformationally fixed Envs, including a 201C 433C (DS) variant specifically recognized by broadly neutralizing antibodies. DS-Env retained nanomolar affinity for the CD4 receptor, with which it formed an asymmetric intermediate: a closed trimer bound by a single CD4 without the typical antigenic hallmarks of CD4 induction. Antigenicity-guided structural design can thus be used both to delineate mechanism and to fix conformation, with DS-Env trimers in virus-like-particle and soluble formats providing a new generation of vaccine antigens.
Organizational Affiliation: 
Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.