title: Identification of the principal neutralizing determinant of human immunodeficiency virus type 1 as a fusion domain.
abstract: The V3 loop, located near the middle of the surface envelope glycoprotein gp120, is the major neutralizing domain of human immunodeficiency virus type 1 (HIV-1). Although the majority of the V3 loop is highly variable between different strains of HIV-1, a Gly-Pro-Gly-Arg motif at the tip of the loop is highly conserved. To determine whether this region plays a role in fusion mediated by the HIV-1 envelope glycoproteins, we introduced seven single-amino-acid changes in the V3 loop. The mutant envelope glycoproteins were expressed from an HIV-1 envelope expression vector and analyzed for their ability to induce cell fusion in the absence of virus replication. Our results indicated that single-amino-acid changes in the V3 loop were capable of completely abolishing or greatly reducing the ability of the HIV-1 envelope glycoproteins to induce cell fusion, thereby identifying the V3 loop as a fusion domain of HIV-1. Mutations in the highly conserved tip of the loop or in a nonconserved region flanking the highly conserved tip had no effect on envelope glycoprotein synthesis, processing, transport, or binding to the CD4 receptor molecule. Mutation of the putative disulfide bridge-forming Cys at residue 336 blocked gp160 cleavage and CD4 binding.
authors.affiliation: McArdle Laboratory for Cancer Research, University of Wisconsin, Madison 53706.
authors.forename: E O
authors.initials: EO
authors.lastname: Freed
authors.forename: D J
authors.initials: DJ
authors.lastname: Myers
authors.forename: R
authors.initials: R
authors.lastname: Risser
mesh_terms: D000595:Amino Acid Sequence; D015704:CD4 Antigens / Q000276:immunology; D015699:HIV Envelope Protein gp120 / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics* / Q000276:immunology; D006367:HeLa Cells / Q000276:immunology; D006801:Humans; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009500:Neutralization Tests; D015183:Restriction Mapping; D014162:Transfection; D014759:Viral Envelope Proteins / Q000235:genetics / Q000276:immunology
chemical_list: D015704:CD4 Antigens; D015699:HIV Envelope Protein gp120; D014759:Viral Envelope Proteins