title: Effect of amino acid substitution of the V3 and bridging sheet residues in human immunodeficiency virus type 1 subtype C gp120 on CCR5 utilization.
abstract: The V3 loop and the bridging sheet domain of human immunodeficiency virus type 1 (HIV-1) subtype B envelope glycoprotein gp120 have been implicated in CCR5 coreceptor utilization. In this study, mutant envelope glycoproteins of a subtype C isolate containing substitutions in the V3 or C4 region were generated to determine which are required for efficient CCR5-dependent cell fusion and viral entry. We found that the V3 crown and C4 residues are relatively dispensable for cell-cell fusion, although some residues may be involved in the regulation of early postentry steps in viral replication. In contrast, seven highly conserved residues located in the V3 stem are critical for CCR5 utilization, which can explain the apparent paradox that the functional convergence in CCR5 usage by genetically divergent HIV-1 strains involves a variable region. The finding that C4 residues do not have a critical role may appear to contradict the current model that bridging sheet residues are involved in the gp120-CCR5 interaction. However, a plausible interpretation is that these C4 residues may have a distinct role in the binding and fusion steps of the gp120-CCR5 interaction.
authors.affiliation: Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts 02115, USA.
authors.forename: Pirada
authors.initials: P
authors.lastname: Suphaphiphat
authors.forename: Arunee
authors.initials: A
authors.lastname: Thitithanyanont
authors.forename: Saowakon
authors.initials: S
authors.lastname: Paca-Uccaralertkun
authors.forename: Max
authors.initials: M
authors.lastname: Essex
authors.forename: Tun-Hou
authors.initials: TH
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D002459:Cell Fusion; D002460:Cell Line; D004279:DNA, Viral / Q000378:metabolism; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D006801:Humans; D010446:Peptide Fragments / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011533:Proviruses; D019713:Receptors, CCR5 / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014771:Virion / Q000378:metabolism; D016662:Virus Integration
chemical_list: D004279:DNA, Viral; D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments; D019713:Receptors, CCR5; D011993:Recombinant Fusion Proteins