We have developed an improved method for visualizing actin filament polarity in thin sections. Myosin subfragment-1 (S-1)-decorated actin filaments display a dramatically enhanced arrowhead configuration when fixed in a medium which contains 0.2 % tannic acid. With the exception of brush borders from intestinal epithelial cells, the arrowhead periodicity of decorated filaments in a variety of nonmuscle cells is similar to that in isolated myofibrils. The periodicity of decorated filaments in brush borders is significantly smaller. Actin filaments which attach to membranes display a clear, uniform polarity, with the S-1 arrowheads pointing away from the plasma membrane, while those which comprise the stress fibers of myoblasts and CHO cells have antiparallel polarities. These observations are consistent with a sliding filament mechanism of cell motility.
The visualization of actin filament polarity in thin sections. Evidence for the uniform polarity of membrane-associated filaments.
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D A Begg, R Rodewald, L I Rebhun; The visualization of actin filament polarity in thin sections. Evidence for the uniform polarity of membrane-associated filaments.. J Cell Biol 1 December 1978; 79 (3): 846–852. doi: https://doi.org/10.1083/jcb.79.3.846
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