Cholesterol Promotes Protein Binding by Affecting Membrane Electrostatics and Solvation Properties

Milka Doktorova, Frederick A. Heberle, Richard L. Kingston, George Khelashvili, Michel A. Cuendet, Yi Wen, John Katsaras, Gerald W. Feigenson, Volker M. Vogt, Robert A. Dick

Research output: Contribution to journalArticlepeer-review

34 Scopus citations

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.

Original languageEnglish
Pages (from-to)2004-2015
Number of pages12
JournalBiophysical Journal
Volume113
Issue number9
DOIs
StatePublished - Nov 7 2017

Funding

This work was supported by National Institutes of Health (NIH) grant R01GM107013 (to V.M.V.), National Institutes of Health (NIH) grant R01GM105684 (to G.W.F.), and National Institutes of Health (NIH) grant PO1DA012408 (for M.D., G.K., and M.A.C.). The work at Oak Ridge National Laboratory’s EQ-SANS instrument at the Spallation Neutron Source was sponsored by the Basic Energy Science (BES) Program , Office of Science , US Department of Energy (DOE) under contract no. DEAC05-00OR22725 with UT-Battelle. J.K. is supported through the Scientific User Facilities Division of the Department of Energy (DOE) Office of Science .

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