title: Myosin from pancreatic acinar carcinoma cells. Isolation, characterization and demonstration of heavy- and light-chain phosphorylation.
abstract: Myosin has been identified in a variety of non-muscle cells, and is believed to play a role in maintenance of cell shape, locomotion, cytokinesis, exocytosis and other cellular functions. In this paper we describe the purification of myosin from a pancreatic acinar-cell carcinoma of the rat which forms solid tumours, but retains many differentiated functions. The purified myosin was composed of a 200,000 Da heavy chain and two or three classes of light chains. Electron-microscopic examination of rotary-shadowed preparations revealed that individual molecules had two globular heads and a long tail measuring approx. 149 nm. The myosin was soluble in high-salt buffers and became sedimentable as the ionic strength was lowered. Examination of negative-stained preparations showed that this sedimentable myosin consisted of short, bipolar, thick filaments which had a strong tendency to aggregate in a head-to-head manner. The ATPase activity of the purified myosin was stimulated by EDTA or Ca2+, but not by Mg2+. In low ionic strength the Mg2+-dependent ATPase activity was activated by muscle f-actin. The pancreatic myosin bound to actin and could be dissociated by the addition of MgATP. Myosin purified from cells cultured in media containing [32P]Pi was phosphorylated on one of the light chains as well as the heavy chain. Thus pancreatic acinar cells contain a typical non-muscle myosin, and the subunits of this molecule are subject to post-translational modification by phosphorylation.
mesh_terms: D000199:Actins / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D002277:Carcinoma / Q000201:enzymology / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D008297:Male; D008854:Microscopy, Electron; D009218:Myosins / Q000302:isolation & purification / Q000378:metabolism*; D010190:Pancreatic Neoplasms / Q000201:enzymology / Q000378:metabolism*; D010766:Phosphorylation; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D000199:Actins; D011189:Potassium Chloride; D000251:Adenosine Triphosphatases; D009218:Myosins