The stoichiometry of trimeric SIV glycoprotein interaction with CD4 differs from that of anti-envelope antibody Fab fragments

Kim, M., Chen, B., Hussey, R.E., Chishti, Y., Montefiori, D., Hoxie, J.A., Byron, O. , Campbell, G., Harrison, S.C. and Reinherz, E.L. (2001) The stoichiometry of trimeric SIV glycoprotein interaction with CD4 differs from that of anti-envelope antibody Fab fragments. Journal of Biological Chemistry, 276(46), pp. 42667-42676. (doi: 10.1074/jbc.m104166200) (PMID:11544255)

Abstract

Human and simian immunodeficiency viruses infect host lymphoid cells by binding CD4 molecules via their gp160 envelope glycoproteins. Biochemical studies on recombinant SIVmac32H (pJ5) envelope ectodomain gp140 precursor protein show that the envelope is a trimer. Using size exclusion chromatography, quantitative amino acid analysis, analytical ultracentrifugation, and CD4-based competition assay, we demonstrate that the stoichiometry of CD4 receptor-oligomeric envelope interaction is 1:1. By contrast, Fab fragments of both neutralizing and non-neutralizing monoclonal antibodies bind at a 3:1 ratio. Thus, despite displaying equivalent CD4 binding sites on each of the three gp140 protomers within an uncleaved trimer, only one site binds the soluble 4-domain human CD4 extracellular segment. The anti-cooperativity and the faster k(off) of gp140 trimer:CD4 versus gp120 monomer:CD4 interaction suggest that CD4-induced conformational change is impeded in the intact envelope. The implications of these findings for immunity against human immunodeficiency virus and simian immunodeficiency virus are discussed.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Byron, Professor Olwyn
• Authors: Kim, M., Chen, B., Hussey, R.E., Chishti, Y., Montefiori, D., Hoxie, J.A., Byron, O., Campbell, G., Harrison, S.C., and Reinherz, E.L.
• College/School: College of Medical Veterinary and Life Sciences > School of Life Sciences
• Journal Name: Journal of Biological Chemistry
• Journal Abbr.: J Biol Chem.
• Publisher: American Society for Biochemistry and Molecular Biology, Inc.
• ISSN: 0021-9258
• ISSN (Online): 1083-351X
• Published Online: 04 January 2001
• Copyright Holders: Copyright © 2001 ASBMB
• First Published: First published in Journal of Biological Chemistry 276(46): 42667-42676
• Publisher Policy: Reproduced under a Creative Commons License