TY - JOUR
T1 - Brownian motion of inert tracer macromolecules in polymerized and spontaneously bundled mixtures of actin and filamin
AU - Hou, L.
AU - Luby-Phelps, K.
AU - Lanni, F.
PY - 1990
Y1 - 1990
N2 - By use of light microscopy and fluorescence photobleaching recovery, we have studied (a) structures that form in a system composed of copolymerized rabbit muscle actin and chicken gizzard filamin and (b) the Brownian motion of inert tracer macromolecules in this matrix. We have used as tracers size-fractionated fluorescein-labeled ficoll and submicron polystyrene latex particles. In F-actin solutions, the relative diffusion coefficient of the tracer was a decreasing function of both tracer size and actin concentration. Also, a percolation transition for latex particle mobility was found to follow a form suggested by Ogston (Ogston, A.G. 1958. Trans. Faraday Soc. 54:1754-1757) for random filament matrices. The inclusion of filamin before polymerization resulted in increased tracer mobility. Below a filamin dimer-to-actin monomer ratio of 1:140, no structural features were observed in the light microscope. At or above this ratio for all actin concentrations tested, a three-dimensional network of filament bundles was clearly discriminated. Latex particles were always excluded from the bundles. By use of a dialysis optical cell in which polymerization could be initiated with very little hydrodynamic stress, we found that filamin can spontaneously bundle F-actin. A simple physical picture explains how dynamics can affect the structural result of coassembly and provides a further hypothesis on the balance between random filament cross-linking and large-scale bundling. Control of this balance may be important in cytoplasmic motile events.
AB - By use of light microscopy and fluorescence photobleaching recovery, we have studied (a) structures that form in a system composed of copolymerized rabbit muscle actin and chicken gizzard filamin and (b) the Brownian motion of inert tracer macromolecules in this matrix. We have used as tracers size-fractionated fluorescein-labeled ficoll and submicron polystyrene latex particles. In F-actin solutions, the relative diffusion coefficient of the tracer was a decreasing function of both tracer size and actin concentration. Also, a percolation transition for latex particle mobility was found to follow a form suggested by Ogston (Ogston, A.G. 1958. Trans. Faraday Soc. 54:1754-1757) for random filament matrices. The inclusion of filamin before polymerization resulted in increased tracer mobility. Below a filamin dimer-to-actin monomer ratio of 1:140, no structural features were observed in the light microscope. At or above this ratio for all actin concentrations tested, a three-dimensional network of filament bundles was clearly discriminated. Latex particles were always excluded from the bundles. By use of a dialysis optical cell in which polymerization could be initiated with very little hydrodynamic stress, we found that filamin can spontaneously bundle F-actin. A simple physical picture explains how dynamics can affect the structural result of coassembly and provides a further hypothesis on the balance between random filament cross-linking and large-scale bundling. Control of this balance may be important in cytoplasmic motile events.
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U2 - 10.1083/jcb.110.5.1645
DO - 10.1083/jcb.110.5.1645
M3 - Article
C2 - 2110570
AN - SCOPUS:0025292782
SN - 0021-9525
VL - 110
SP - 1645
EP - 1654
JO - Journal of Cell Biology
JF - Journal of Cell Biology
IS - 5
ER -