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Biophys J. 2017 Nov 7;113(9):2004-2015. doi: 10.1016/j.bpj.2017.08.055.

Cholesterol Promotes Protein Binding by Affecting Membrane Electrostatics and Solvation Properties.

Author information

1
Tri-Institutional PhD Program in Computational Biology and Medicine, Weill Cornell Medical College, New York, New York.
2
The Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee; Joint Institute for Biological Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee. Electronic address: heberlefa@ornl.gov.
3
School of Biological Sciences, The University of Auckland, Auckland, New Zealand.
4
Department of Physiology and Biophysics, Weill Cornell Medical College, New York, New York.
5
Department of Biochemistry and Molecular Cell Biology, Cornell University, Ithaca, New York.
6
The Bredesen Center for Interdisciplinary Research and Graduate Education, University of Tennessee, Knoxville, Tennessee; Biology and Soft Matter Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee; Shull Wollan Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee.
7
Department of Biochemistry and Molecular Cell Biology, Cornell University, Ithaca, New York. Electronic address: rad82@cornell.edu.

Abstract

Binding of the retroviral structural protein Gag to the cellular plasma membrane is mediated by the protein's matrix (MA) domain. Prominent among MA-PM interactions is electrostatic attraction between the positively charged MA domain and the negatively charged plasma membrane inner leaflet. Previously, we reported that membrane association of HIV-1 Gag, as well as purified Rous sarcoma virus (RSV) MA and Gag, depends strongly on the presence of acidic lipids and is enhanced by cholesterol (Chol). The mechanism underlying this enhancement was unclear. Here, using a broad set of in vitro and in silico techniques we addressed molecular mechanisms of association between RSV MA and model membranes, and investigated how Chol enhances this association. In neutron scattering experiments with liposomes in the presence or absence of Chol, MA preferentially interacted with preexisting POPS-rich clusters formed by nonideal lipid mixing, binding peripherally to the lipid headgroups with minimal perturbation to the bilayer structure. Molecular dynamics simulations showed a stronger MA-bilayer interaction in the presence of Chol, and a large Chol-driven increase in lipid packing and membrane surface charge density. Although in vitro MA-liposome association is influenced by disparate variables, including ionic strength and concentrations of Chol and charged lipids, continuum electrostatic theory revealed an underlying dependence on membrane surface potential. Together, these results conclusively show that Chol affects RSV MA-membrane association by making the electrostatic potential at the membrane surface more negative, while decreasing the penalty for lipid headgroup desolvation. The presented approach can be applied to other viral and nonviral proteins.

PMID:
29117524
PMCID:
PMC5685651
DOI:
10.1016/j.bpj.2017.08.055
[Indexed for MEDLINE]
Free PMC Article

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