The effect of diffusion on the trapping of membrane-bound receptors by localized coated pits |
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| Authors: | E Peacock-Lopez J A Ramirez |
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| Affiliation: | 1. Department of Chemistry, University of California, Davis, CA 95616, U.S.A.;2. Graduate Group in Biophysics, University of California, Davis, CA 95616, U.S.A.;1. Max Planck Institute of Biophysics, Mechanisms of Cellular Quality Control, Frankfurt a. M., Germany;2. University of Geneva, Department of Biochemistry, Geneva, Switzerland;3. University of Texas at Austin, Department of Biomedical Engineering, USA;4. University of Texas at Austin, Department of Chemical Engineering, USA;1. Laboratory of Neural Membrane Biology, Graduate School of Brain Science, Doshisha University, Kyoto 610-0394, Japan;2. Department of Pharmacology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan;3. International Research Center for Neurointelligence (WPI-IRCN), The University of Tokyo, Tokyo 113-0033, Japan;4. Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, Tokyo 113-0033, Japan |
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| Abstract: | Localized coated pits are considered in the primary steps of receptor-mediated endocytosis. According to the pit reinsertion mechanism, we have modified our previous kinetic model and studied the effect of diffusion on the trapping rate constant (k+). Using experimental data for low density lipoprotein (LDL) receptors on fibroblast cells, we found that the binding of receptors to coated pits is not totally diffusion controlled. For example, the process is less than 78% diffusion controlled if receptors are not allowed to escape the coated pits. However, due to the large uncertainties in the experimental parameters, a diffusion-controlled process cannot be ruled out. The greatest differences between localized and random reinsertion were found when the escaping rate constant (k-) is much greater than the rate constant for invagination of the pits (lambda 1). Under this condition, k+ for localized reinsertion is no less than 39% diffusion controlled, while k+ for random reinsertion shows no diffusion effect at all. |
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