Conditional trimerization and lytic activity of HIV-1 gp41 variants containing the membrane-associated segments

Zhou Dai, Yisong Tao, Nina Liu, Michael D. Brenowitz, Mark E. Girvin, Jonathan R. Lai

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Fusion of host and viral membranes is a critical step during infection by membrane-bound viruses. The HIV-1 glycoproteins gp120 (surface subunit) and gp41 (fusion subunit) represent the prototypic system for studying this process; in the prevailing model, the gp41 ectodomain forms a trimeric six-helix bundle that constitutes a critical intermediate and provides the energetic driving force for overcoming barriers associated with membrane fusion. However, most structural studies of gp41 variants have been performed either on ectodomain constructs lacking one or more of the membrane-associated segments (the fusion peptide, FP, the membrane-proximal external region, MPER, and the transmembrane domain, TM) or on variants consisting of these isolated segments alone without the ectodomain. Several recent reports have suggested that the HIV-1 ectodomain, as well as larger construct containing the membrane-bound segments, dissociates from a trimer to a monomer in detergent micelles. Here we compare the properties of a series of gp41 variants to delineate the roles of the ectodomain, FP, and MPER and TM, all in membrane-mimicking environments. We find that these proteins are prone to formation of a monomer in detergent micelles. In one case, we observed exclusive monomer formation at pH 4 but conditional trimerization at pH 7 even at low micromolar (5 M) protein concentrations. Liposome release assays demonstrate that these gp41-related proteins have the capacity to induce content leakage but that this activity is also strongly modulated by pH with much higher activity at pH 4. Circular dichroism, nuclear magnetic resonance, and binding assays with antibodies specific to the MPER provide insight into the structural and functional roles of the FP, MPER, and TM and their effect on structure within the larger context of the fusion subunit.

Original languageEnglish (US)
Pages (from-to)1589-1599
Number of pages11
JournalBiochemistry
Volume54
Issue number8
DOIs
StatePublished - Mar 3 2015

Fingerprint

HIV-1
Membranes
Fusion reactions
Micelles
Detergents
Monomers
Virus Internalization
Proteins
Membrane Fusion
Assays
Membrane Glycoproteins
Circular Dichroism
Liposomes
Magnetic Resonance Spectroscopy
Viruses
Peptides
Glycoproteins
Antibodies
Nuclear magnetic resonance
Infection

ASJC Scopus subject areas

  • Biochemistry

Cite this

Conditional trimerization and lytic activity of HIV-1 gp41 variants containing the membrane-associated segments. / Dai, Zhou; Tao, Yisong; Liu, Nina; Brenowitz, Michael D.; Girvin, Mark E.; Lai, Jonathan R.

In: Biochemistry, Vol. 54, No. 8, 03.03.2015, p. 1589-1599.

Research output: Contribution to journalArticle

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