The visualization of actin filament polarity in thin sections. Evidence for the uniform polarity of membrane-associated filaments.
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.
D000199:Actins / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002465:Cell Movement; D003593:Cytoplasm / Q000648:ultrastructure*; D003599:Cytoskeleton / Q000502:physiology / Q000648:ultrastructure*; D004848:Epithelium / Q000648:ultrastructure; D005260:Female; D005404:Fixatives; D047348:Hydrolyzable Tannins; D007583:Jejunum / Q000648:ultrastructure; D008871:Microvilli / Q000648:ultrastructure; D009218:Myosins / Q000378:metabolism; D010063:Ovum / Q000648:ultrastructure; D051381:Rats; D012617:Sea Urchins
D000199:Actins; D005404:Fixatives; D047348:Hydrolyzable Tannins; D009218:Myosins