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J Mol Biol. 2016 Apr 24;428(8):1637-55. doi: 10.1016/j.jmb.2016.03.005. Epub 2016 Mar 16.

Structural and Molecular Determinants of Membrane Binding by the HIV-1 Matrix Protein.

Author information

1
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA.
2
Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute at Fredrick, Fredrick, MD 21702-1201, USA.
3
Institut des Biomolécules Max Mousseron, CNRS UMR5247, Université Montpellier, Faculté de Pharmacie, Montpellier Cedex 05, France.
4
Centre d'études d'agents Pathogénes et Biotechnologies pour la Santé CNRS-UMR 5236, Université Montpellier, Montpellier Cedex 5, France.
5
Department of Biochemistry, Center for Structural Biology, and Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37240-7917, USA.
6
Virus-Cell Interaction Section, HIV Dynamics and Replication Program, National Cancer Institute at Fredrick, Fredrick, MD 21702-1201, USA. Electronic address: efreed@mail.nih.gov.
7
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA. Electronic address: janm@umbc.edu.
8
Department of Chemistry and Biochemistry, Howard Hughes Medical Institute, University of Maryland, Baltimore County, Baltimore, MD 21250, USA. Electronic address: summers@hhmi.umbc.edu.

Abstract

Assembly of HIV-1 particles is initiated by the trafficking of viral Gag polyproteins from the cytoplasm to the plasma membrane, where they co-localize and bud to form immature particles. Membrane targeting is mediated by the N-terminally myristoylated matrix (MA) domain of Gag and is dependent on the plasma membrane marker phosphatidylinositol-4,5-bisphosphate [PI(4,5)P2]. Recent studies revealed that PI(4,5)P2 molecules containing truncated acyl chains [tr-PI(4,5)P2] are capable of binding MA in an "extended lipid" conformation and promoting myristoyl exposure. Here we report that tr-PI(4,5)P2 molecules also readily bind to non-membrane proteins, including HIV-1 capsid, which prompted us to re-examine MA-PI(4,5)P2 interactions using native lipids and membrane mimetic liposomes and bicelles. Liposome binding trends observed using a recently developed NMR approach paralleled results of flotation assays, although the affinities measured under the equilibrium conditions of NMR experiments were significantly higher. Native PI(4,5)P2 enhanced MA binding to liposomes designed to mimic non-raft-like regions of the membrane, suggesting the possibility that binding of the protein to disordered domains may precede Gag association with, or nucleation of, rafts. Studies with bicelles revealed a subset of surface and myr-associated MA residues that are sensitive to native PI(4,5)P2, but cleft residues that interact with the 2'-acyl chains of tr-PI(4,5)P2 molecules in aqueous solution were insensitive to native PI(4,5)P2 in bicelles. Our findings call to question extended-lipid MA:membrane binding models, and instead support a model put forward from coarse-grained simulations indicating that binding is mediated predominantly by dynamic, electrostatic interactions between conserved basic residues of MA and multiple PI(4,5)P2 and phosphatidylserine molecules.

KEYWORDS:

HIV-1 matrix protein; PIP2; bicelles; membrane targeting; polysomes

PMID:
26992353
PMCID:
PMC4836608
DOI:
10.1016/j.jmb.2016.03.005
[Indexed for MEDLINE]
Free PMC Article

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