Glycoprotein exposed on the surface of the HIV virus
Envelope glycoprotein GP120 (or gp120 ) is a glycoprotein exposed on the surface of the HIV envelope . It was discovered by Professors Tun-Hou Lee and Myron "Max" Essex of the Harvard School of Public Health in 1984.[ 1] The 120 in its name comes from its molecular weight of 120 kDa . Gp120 is essential for virus entry into cells as it plays a vital role in attachment to specific cell surface receptors . These receptors are DC-SIGN ,[ 2] Heparan Sulfate Proteoglycan [ 3] and a specific interaction with the CD4 receptor ,[ 4] particularly on helper T-cells . Binding to CD4 induces the start of a cascade of conformational changes in gp120 and gp41 that lead to the fusion of the viral membrane with the host cell membrane . Binding to CD4 is mainly electrostatic although there are van der Waals interactions and hydrogen bonds .[ 5]
Gp120 is coded by the HIV env gene , which is around 2.5 kb long and codes for around 850 amino acids.[ 6] The primary env product is the protein gp160, which gets cleaved to gp120 (~480 amino acids) and gp41 (~345 amino acids) in the endoplasmatic reticulum by the cellular protease furin .[ 7] The crystal structure of core gp120 shows an organization with an outer domain, an inner domain with respect to its termini and a bridging sheet . Gp120 is anchored to the viral membrane , or envelope, via non-covalent bonds with the transmembrane glycoprotein , gp41 . Three gp120s and gp41s combine in a trimer of heterodimers to form the envelope spike,[ 8] which mediates attachment to and entry into the host cell.
^ Sodroski, Joseph; Patarca, Roberto; Perkins, Dennis; Briggs, Debra; Tun-Hou, Lee; Essex, Myron; Coligan, John; Wong-Staal, Flossie; Gallo, Robert C. (1984). "Sequence of the Envelope Glycoprotein Gene of Type II Human T Lymphotropic Virus" . Science . 225 (4660): 421–424. Bibcode :1984Sci...225..421S . doi :10.1126/science.6204380 . PMID 6204380 .
^ Curtis BM, Scharnowske S, Watson AJ (September 1992). "Sequence and expression of a membrane-associated C-type lectin that exhibits CD4-independent binding of human immunodeficiency virus envelope glycoprotein gp120" . Proc. Natl. Acad. Sci. U.S.A . 89 (17): 8356–60. Bibcode :1992PNAS...89.8356C . doi :10.1073/pnas.89.17.8356 . PMC 49917 . PMID 1518869 .
^ de Witte L, Bobardt M, Chatterji U, Degeest G, David G, Geijtenbeek TB, Gallay P (December 2007). "Syndecan-3 is a dendritic cell-specific attachment receptor for HIV-1" . Proc. Natl. Acad. Sci. U.S.A . 104 (49): 19464–9. Bibcode :2007PNAS..10419464D . doi :10.1073/pnas.0703747104 . PMC 2148312 . PMID 18040049 .
^ Dalgleish AG, Beverley PC, Clapham PR, Crawford DH, Greaves MF, Weiss RA (1984). "The CD4 (T4) antigen is an essential component of the receptor for the AIDS retrovirus" . Nature . 312 (5996): 763–7. Bibcode :1984Natur.312..763D . doi :10.1038/312763a0 . PMID 6096719 . S2CID 4349809 .
^ Korkut, A; Hendrickson, WA (2012). "Structural Plasticity and Conformational Transitions of HIV Envelope Glycoprotein gp120" . PLOS ONE . 7 (12): e52170. Bibcode :2012PLoSO...752170K . doi :10.1371/journal.pone.0052170 . PMC 3531394 . PMID 23300605 .
^ Kuiken, C., Leitner, T., Foley, B., et al. (2008). "HIV Sequence Compendium" , Los Alamos National Laboratory.
^ Hallenberger S, Bosch V, Angliker H, Shaw E, Klenk HD, Garten W (November 1992). "Inhibition of furin-mediated cleavage activation of HIV-1 glycoprotein gp160". Nature . 360 (6402): 358–61. Bibcode :1992Natur.360..358H . doi :10.1038/360358a0 . PMID 1360148 . S2CID 4306605 .
^ Zhu P, Winkler H, Chertova E, Taylor KA, Roux KH (November 2008). "Cryoelectron tomography of HIV-1 envelope spikes: further evidence for tripod-like legs" . PLOS Pathog . 4 (11): e1000203. doi :10.1371/journal.ppat.1000203 . PMC 2577619 . PMID 19008954 .