title: Effects of the I559P gp41 change on the conformation and function of the human immunodeficiency virus (HIV-1) membrane envelope glycoprotein trimer.
abstract: The mature human immunodeficiency virus (HIV-1) envelope glycoprotein (Env) trimer is produced by proteolytic cleavage of a precursor and consists of three gp120 exterior and three gp41 transmembrane subunits. The metastable Env complex is induced to undergo conformational changes required for virus entry by the binding of gp120 to the receptors, CD4 and CCR5/CXCR4. An isoleucine-to-proline change (I559P) in the gp41 ectodomain has been used to stabilize soluble forms of HIV-1 Env trimers for structural characterization and for use as immunogens. In the native membrane-anchored HIV-1BG505 Env, the I559P change modestly decreased proteolytic maturation, increased the non-covalent association of gp120 with the Env trimer, and resulted in an Env conformation distinctly different from that of the wild-type HIV-1BG505 Env. Compared with the wild-type Env, the I559P Env was recognized inefficiently by polyclonal sera from HIV-1-infected individuals, by several gp41-directed antibodies, by some antibodies against the CD4-binding site of gp120, and by antibodies that preferentially recognize the CD4-bound Env. Some of the gp120-associated antigenic differences between the wild-type HIV-1BG505 Env and the I559P mutant were compensated by the SOS disulfide bond between gp120 and gp41, which has been used to stabilize cleaved soluble Env trimers. Nonetheless, regardless of the presence of the SOS changes, Envs with proline 559 were recognized less efficiently than Envs with isoleucine 559 by the VRC01 neutralizing antibody, which binds the CD4-binding site of gp120, and the PGT151 neutralizing antibody, which binds a hybrid gp120-gp41 epitope. The I559P change completely eliminated the ability of the HIV-1BG505 Env to mediate cell-cell fusion and virus entry, and abolished the capacity of the SOS Env to support virus infection in the presence of a reducing agent. These results suggest that differences exist between the quaternary structures of functional Env spikes and I559P Envs.
authors: Department of Microbiology and Immunology, McGill University, Montreal, H3A 2B4 Quebec, Canada; Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, H2X 0A9, Québec, Canada.
authors: Nirmin
authors: N
authors: Alsahafi
authors: Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, H2X 0A9, Québec, Canada; Department of Microbiology, Infectiology and Immunology, Université de Montréal, Montréal, H3C 3J7 Quebec, Canada.
authors: Olfa
authors: O
authors: Debbeche
authors: Department of Cancer Immunology and AIDS, Dana-Farber Cancer Institute, Boston, Massachusetts, 02115, United States of America; Department of Microbiology & Immunobiology, Harvard Medical School, Boston, Massachusetts, 02115, United States of America; Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, 02115, United States of America.
authors: Joseph
authors: J
authors: Sodroski
authors: Department of Microbiology and Immunology, McGill University, Montreal, H3A 2B4 Quebec, Canada; Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Montréal, H2X 0A9, Québec, Canada; Department of Microbiology, Infectiology and Immunology, Université de Montréal, Montréal, H3C 3J7 Quebec, Canada.
authors: Andrés
authors: A
authors: Finzi
mesh_terms: D057134:Antibodies, Neutralizing / Q000276:immunology; D015704:CD4 Antigens / Q000737:chemistry / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D057809:HEK293 Cells; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000378:metabolism; D015700:HIV Envelope Protein gp41 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000378:metabolism*; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D053586:Virus Internalization
chemical_list: D057134:Antibodies, Neutralizing; D015704:CD4 Antigens; D004220:Disulfides; D015699:HIV Envelope Protein gp120; D015700:HIV Envelope Protein gp41