Schematic of membrane-mediated interactions between chemoreceptor trimers.

<p>(A) If the hydrophobic thickness of the unperturbed lipid monolayer, , does not match the hydrophobic thickness of chemoreceptor trimers, , the lipid bilayer locally deforms in the vicinity of chemoreceptor trimers, yielding membrane-mediated interactions between trimers. (B) The three-fold symmetry of chemoreceptor trimers induces directionality of membrane-mediated interactions between trimers. The trimer configurations in the left and right panels correspond to tip-on and face-on orientations, respectively, with thickness deformations of the bilayer membrane in the vicinity of trimers illustrated by density maps (see <a href="http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.1003932#pcbi.1003932.s002" target="_blank">S2 Figure</a> for a three-dimensional illustration of thickness deformations). We denote by the center-to-center distance between trimers. In our calculations, we used chemoreceptor trimers of the indicated perturbed cylindrical shape with width nm.