title: Membrane stiffness is modified by integral membrane proteins.
abstract: The ease with which a cell membrane can bend and deform is important for a wide range of biological functions. Peripheral proteins that induce curvature in membranes (e.g. BAR domains) have been studied for a number of years. Little is known, however, about the effect of integral membrane proteins on the stiffness of a membrane (characterised by the bending rigidity, Kc). We demonstrate by computer simulation that adding integral membrane proteins at physiological densities alters the stiffness of the membrane. First we establish that the coarse-grained MARTINI forcefield is able to accurately reproduce the bending rigidity of a small patch of 1500 phosphatidyl choline lipids by comparing the calculated value to both experiment and an atomistic simulation of the same system. This enables us to simulate the dynamics of large (ca. 50 000 lipids) patches of membrane using the MARTINI coarse-grained description. We find that altering the lipid composition changes the bending rigidity. Adding integral membrane proteins to lipid bilayers also changes the bending rigidity, whilst adding a simple peripheral membrane protein has no effect. Our results suggest that integral membrane proteins can have different effects, and in the case of the bacterial outer membrane protein, BtuB, the greater the density of protein, the larger the reduction in stiffness.
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK. mark.sansom@bioch.ox.ac.uk.
authors.forename: Philip W
authors.identifier: http://orcid.org/0000-0003-0912-4483
authors.initials: PW
authors.lastname: Fowler
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK. mark.sansom@bioch.ox.ac.uk.
authors.forename: Jean
authors.initials: J
authors.lastname: Hélie
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK. mark.sansom@bioch.ox.ac.uk.
authors.forename: Anna
authors.initials: A
authors.lastname: Duncan
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK. mark.sansom@bioch.ox.ac.uk.
authors.forename: Matthieu
authors.initials: M
authors.lastname: Chavent
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK. mark.sansom@bioch.ox.ac.uk.
authors.forename: Heidi
authors.initials: H
authors.lastname: Koldsø
authors.affiliation: Department of Biochemistry, University of Oxford, South Parks Rd, Oxford, OX1 3QU, UK. mark.sansom@bioch.ox.ac.uk.
authors.forename: Mark S P
authors.initials: MS
authors.lastname: Sansom
mesh_terms: D002462:Cell Membrane / Q000737:chemistry*; D003198:Computer Simulation; D008051:Lipid Bilayers / Q000737:chemistry; D008565:Membrane Proteins / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D010713:Phosphatidylcholines / Q000737:chemistry*
chemical_list: D008051:Lipid Bilayers; D008565:Membrane Proteins; D010713:Phosphatidylcholines