title: Actin in Triton-insoluble cytoskeleton of thyroid.
abstract: Treatment of bovine thyroid with the non-ionic detergent Triton X-100 extracts most of the cell protein and leaves insoluble residue. This Triton-insoluble cytoskeleton consists of five major polypeptides on sodium dodecyl sulfate polyacrylamide gels. One of these polypeptides is actin. Based on DNase inhibition assay, 30% of the total actin is associated with the cytoskeleton as the filamentous form. Thyroid actin from the cytoskeleton has been solubilized by dialysis against a low ionic strength buffer at pH 8.0 and purified to homogeneity by a polymerizing-depolymerizing cycle. The overall purification was about 144-fold with a yield of 10%. Bovine thyroid actin is very similar to actins from other tissues on the basis of: (1) comigration with rabbit skeletal muscle actin during gel electrophoresis in sodium dodecyl sulfate, (2) its amino acid composition, which includes about 1 mole of 3-methylhistidine per 42,000 g, (3) its ability to bind and inhibit pancreatic deoxyribonuclease I, and (4) its ability to form 7-8 nm microfilaments which is similar to that of skeletal filamentous actin. Thyroid actin contains beta- and gamma-isoactins, with isoelectric points more alkaline than the alpha-actin of rabbit skeletal muscle.
mesh_terms: D000199:Actins / Q000032:analysis*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D002458:Cell Fractionation; D002846:Chromatography, Affinity; D003599:Cytoskeleton / Q000032:analysis*; D003850:Deoxyribonuclease I; D003851:Deoxyribonucleases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D004720:Endonucleases / Q000378:metabolism; D007525:Isoelectric Focusing; D008854:Microscopy, Electron; D017830:Octoxynol; D011092:Polyethylene Glycols; D012995:Solubility; D013961:Thyroid Gland / Q000166:cytology*
chemical_list: D000199:Actins; D000596:Amino Acids; D011092:Polyethylene Glycols; D017830:Octoxynol; D003851:Deoxyribonucleases; D004720:Endonucleases; D003850:Deoxyribonuclease I