Differences among 100-A filamentilament subunits from different cell types.
The protein subunit of 100-A filaments constitutes approximately 50% of the cytoskeleton protein of chick fibroblasts. In addition to the 43,000-dalton protein (constitutive actin) common to all cell types, fibroblast cytoskeletons contain a 58,000-dalton protein likely to be the 100-A filament subunit, whereas smooth muscle contains, instead, a 55,000-dalton protein. Additional differences among 100-A filaments are shown by immunofluorescence using antibodies angainst chick fibroblast 58,000-dalton component (anti-F58K) and against chick brain 100-A filament subunits (anti-BF). Anti-F58K binds to 100-A filaments in chick fibroblasts, presumptive myoblasts, chondroblasts, pigment cells, and neurons, but not to 100-A filaments in mouse or human fibroblasts. This antibody stains cables of 100-A filaments induced by sequentially treating cells with cytochalasin B and Colcemid. Anti-BF binds only to neurofilaments and not to 100-A filaments of other cell types studied. Absorption or antibodies with purified subunits from gizzard 100-A filaments eliminates binding of anti-F58K to the filaments of all cell types but does not diminish binding of anti-BF to neurofilaments. Various IgGs also bind nonspecifically to induced cables of 100-A filaments. The problem of nonspecific binding of labeled antibodies, as well as the problem of cell and species specificity of the 100-A filaments, is discussed.
D000199:Actins / Q000378:metabolism; D001921:Brain / Q000648:ultrastructure; D002478:Cells, Cultured; D003571:Cytochalasin B / Q000494:pharmacology; D003593:Cytoplasm; D003703:Demecolcine / Q000494:pharmacology; D005455:Fluorescent Antibody Technique; D008970:Molecular Weight; D009124:Muscle Proteins / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism
D000199:Actins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D003571:Cytochalasin B; D003703:Demecolcine