The protein subunit of 100-Ȧ 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-Ȧ filament subunit, whereas smooth muscle contains, instead, a 55,000-dalton protein. Additional differences among 100-Ȧ filaments are shown by immunofluorescence using antibodies against chick fibroblast 58,000-dalton component (anti-F58K) and against chick brain 100-Ȧ filament subunits (anti-BF). Anti-F58K binds to 100-Ȧ filaments in chick fibroblasts, presumptive myoblasts, chondroblasts, pigment cells, and neurons, but not to 100-Ȧ filaments in mouse or human fibroblasts. This antibody stains cables of 100-Ȧ filaments induced by sequentially treating cells with cytochalasin B and Colcemid. Anti-BF binds only to neurofilaments and not to 100-Ȧ filaments of other cell types studied. Absorption of antibodies with purified subunits from gizzard 100-Ȧ 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-Ȧ filaments. The problem of nonspecific binding of labeled antibodies, as well as the problem of cell and species specificity of the 100-Ȧ filaments, is discussed.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Jan 1 1978|
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