TY - JOUR
T1 - Weak dependence of mobility of membrane protein aggregates on aggregate size supports a viscous model of retardation of diffusion
AU - Kucik, Dennis F.
AU - Elson, Elliot L.
AU - Sheetz, Michael P.
N1 - Funding Information:
This work was supported by National Institutes of Health grants to Elliot L. Elson and Michael P. Sheetz, and a Department of Veterans’ Affairs grant to Dennis F. Kucik.
PY - 1999/1
Y1 - 1999/1
N2 - Proteins in plasma membranes diffuse more slowly than proteins inserted into artificial lipid bilayers. On a long-range scale (>250 nm), submembrane barriers, or skeleton fences that hinder long-range diffusion and create confinement zones, have been described. Even within such confinement zones, however, diffusion of proteins is much slower than predicted by the viscosity of the lipid. The cause of this slowing of diffusion on the micro scale has not been determined and is the focus of this paper. One way to approach this question is to determine the dependence of particle motion on particle size. Some current models predict that the diffusion coefficient of a membrane protein aggregate will depend strongly on its size, while others do not. We have measured the diffusion coefficients of membrane glycoprotein aggregates linked together by concanavalin A molecules bound to beads of various sizes, and also the diffusion coefficients of individual concanavalin A binding proteins. The measurements demonstrate at most a weak dependence of diffusion coefficient on aggregate size. This finding supports retardation by viscous effects, and is not consistent with models involving direct interaction of diffusing proteins with cytoskeletal elements.
AB - Proteins in plasma membranes diffuse more slowly than proteins inserted into artificial lipid bilayers. On a long-range scale (>250 nm), submembrane barriers, or skeleton fences that hinder long-range diffusion and create confinement zones, have been described. Even within such confinement zones, however, diffusion of proteins is much slower than predicted by the viscosity of the lipid. The cause of this slowing of diffusion on the micro scale has not been determined and is the focus of this paper. One way to approach this question is to determine the dependence of particle motion on particle size. Some current models predict that the diffusion coefficient of a membrane protein aggregate will depend strongly on its size, while others do not. We have measured the diffusion coefficients of membrane glycoprotein aggregates linked together by concanavalin A molecules bound to beads of various sizes, and also the diffusion coefficients of individual concanavalin A binding proteins. The measurements demonstrate at most a weak dependence of diffusion coefficient on aggregate size. This finding supports retardation by viscous effects, and is not consistent with models involving direct interaction of diffusing proteins with cytoskeletal elements.
UR - http://www.scopus.com/inward/record.url?scp=0032946242&partnerID=8YFLogxK
U2 - 10.1016/S0006-3495(99)77198-5
DO - 10.1016/S0006-3495(99)77198-5
M3 - Article
C2 - 9876143
AN - SCOPUS:0032946242
SN - 0006-3495
VL - 76
SP - 314
EP - 322
JO - Biophysical Journal
JF - Biophysical Journal
IS - 1 I
ER -