Figure 1.

(a) Schematic illustration of the membrane tube formation as observed experimentally on GUVs (31). The protein-coated domain, for which the proteins are shown as blue spheres, is completely consumed by the protruding tube. The size of the vesicle and the tube are drawn to scale to illustrate a ratio between the protrusion height L and the crowded domain A_c that is representative of the order of magnitude found in experiments (31). (b) Qualitative representation of membrane shapes observed experimentally by Shurer et al. (27) on cells with glycocalyx biopolymers with increasing polymer density. (c) The membrane shape is parameterized by the arc length S and the azimuthal angle ψ, where we treat the membrane as axially symmetrical around the z axis. The proteins that bind to the membrane within an area A_c are modeled as spheres with a radius r_p.