Format

Send to

Choose Destination
Proc Natl Acad Sci U S A. 2019 Nov 5;116(45):22556-22566. doi: 10.1073/pnas.1912427116. Epub 2019 Oct 17.

Topological analysis of the gp41 MPER on lipid bilayers relevant to the metastable HIV-1 envelope prefusion state.

Author information

1
Laboratory of Immunobiology, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115.
2
Department of Medicine, Harvard Medical School, Boston, MA 02115.
3
National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32306.
4
Department of Physics, Florida State University, Tallahassee, FL 32306.
5
Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115.
6
Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, MA 02215.
7
Laboratory of Immunobiology, Department of Medical Oncology, Dana-Farber Cancer Institute, Boston, MA 02115; ellis_reinherz@dfci.harvard.edu Mikyung_Kim@dfci.harvard.edu.
8
Department of Dermatology, Harvard Medical School, Boston, MA 02215.

Abstract

The membrane proximal external region (MPER) of HIV-1 envelope glycoprotein (gp) 41 is an attractive vaccine target for elicitation of broadly neutralizing antibodies (bNAbs) by vaccination. However, current details regarding the quaternary structural organization of the MPER within the native prefusion trimer [(gp120/41)3] are elusive and even contradictory, hindering rational MPER immunogen design. To better understand the structural topology of the MPER on the lipid bilayer, the adjacent transmembrane domain (TMD) was appended (MPER-TMD) and studied. Membrane insertion of the MPER-TMD was sensitive both to the TMD sequence and cytoplasmic residues. Antigen binding of MPER-specific bNAbs, in particular 10E8 and DH511.2_K3, was significantly impacted by the presence of the TMD. Furthermore, MPER-TMD assembly into 10-nm diameter nanodiscs revealed a heterogeneous membrane array comprised largely of monomers and dimers, as enumerated by bNAb Fab binding using single-particle electron microscopy analysis, arguing against preferential trimeric association of native MPER and TMD protein segments. Moreover, introduction of isoleucine mutations in the C-terminal heptad repeat to induce an extended MPER α-helical bundle structure yielded an antigenicity profile of cell surface-arrayed Env variants inconsistent with that found in the native prefusion state. In line with these observations, electron paramagnetic resonance analysis suggested that 10E8 inhibits viral membrane fusion by lifting the MPER N-terminal region out of the viral membrane, mandating the exposure of residues that would be occluded by MPER trimerization. Collectively, our data suggest that the MPER is not a stable trimer, but rather a dynamic segment adapted for structural changes accompanying fusion.

KEYWORDS:

Env; HIV-1; MPER; nanodiscs; transmembrane domains

PMID:
31624123
PMCID:
PMC6842640
[Available on 2020-04-17]
DOI:
10.1073/pnas.1912427116

Conflict of interest statement

The authors declare no competing interest.

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center