Barrier-free paths of directed protein motion in the erythrocyte plasma membrane.
A model is presented for the steric interaction between a plasma membrane protein and the membrane cytoskeleton in the human erythrocyte. The cytoskeleton is treated as a network of polymer chains attached to a flat bilayer, and the membrane protein is a hemisphere of effective radius R(e) with center on the bilayer edge. The simulation is used to investigate the barrier-free path L for linear guided motion of a protein in the bilayer plane. It is shown that the barrier-free paths of small proteins can be used to extract the effective in-plane diameter of cytoskeletal components. For example, the in-plane diameter of an ankyrin attachment site is found to be approximately 12 nm in the simulation, or twice the computational spectrin diameter. The barrier-free paths of large proteins (R(e) > 23 nm) vanish when the proteins are corralled by the cytoskeleton. For intermediate size proteins, L decreases approximately as L is directly proportional to S-1.4 where S is proportional to the sum of the protein and cytoskeleton chain radii.
Department of Physics, Simon Fraser University, Burnaby, British Columbia, Canada.
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D001665:Binding Sites; D055592:Biophysical Phenomena; D001703:Biophysics; D003198:Computer Simulation; D003599:Cytoskeleton / Q000737:chemistry; D004548:Elasticity; D004910:Erythrocyte Membrane / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000737:chemistry*; D008956:Models, Chemical; D009038:Motion; D011485:Protein Binding
D008565:Membrane Proteins