Myosin in cultured fibroblasts

Myosin was identified in three independently derived cell lines of fibroblasts: normal rat kidney cells, mouse 3T3 cells, and mouse L cells. A quantitative two step procedure for its extraction from as little as 200 mg of cultured fibroblasts (wet weight) was developed. Myosin constitutes from 0.5% to over 3% of the total fibroblast protein. Cell fractionation suggests that the myosin principally resides in the cytoplasm. One virus transformed, normal rat kidney cell line contained one half of the myosin of its NRK parent. Treatment of L cells during culture with N⁶,O² dibutyryl cyclic adenosine 3',5' monophosphate and theophylline had no effect on their myosin content. Actin and tubulin were identified in L cells.