title: Tumoral myosins of Ni3S2-induced rhabdomyosarcomas in rat and rabbit: comparative studies with adult and fetal myosins of skeletal muscle.
abstract: Tumoral myosins were isolated from rat and rabbit rhabdomyosarcomas and compared with normal adult and fetal skeletal myosins. The synthetic filaments, the light-chain composition and the Ca2+ ATP-ase activity were studied. In the presence of Mg2+, normal myosins precipitated as bipolar filaments (0.5 micrometer), fetal and tumoral myosins, however, precipitated as long fusiform filaments (1 to 10 micron). SDS-PAGE revealed that tumoral myosins contain the same light-chains as fetal myosin (25000 and 18000 daltons, L25-L18). The third light-chain of the normal muscle myosin (16000 daltons, L16) was absent. In addition, Urea-PAGE revealed the absence of the phosphorylated form of the L18 in fetal and tumoral myosins. Ca2+ ATPase activity measurements performed in function of the Ca2+ concentration showed similarities between fetal and adult muscle myosins. The Ca2+-ATPase activity of tumoral myosins, however, was very low and slightly activated by increasing the Ca2+ concentration (0.01 to 10 mM). The investigation has shown that fetal and tumoral myosins are identical concerning the ultrastructure of their synthetic filaments and their light-chain composition. This was not so in regard to the Ca2+ ATPase activity. This is probably the result of the expression of a new myosin- or of one of its polypeptides-, which has a different Ca2+-ATPase activity.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008274:Magnesium / Q000494:pharmacology; D009132:Muscles / Q000032:analysis* / Q000196:embryology; D009218:Myosins / Q000032:analysis*; D009532:Nickel; D011817:Rabbits; D051381:Rats; D012208:Rhabdomyosarcoma / Q000032:analysis*; D012513:Sarcoma, Experimental / Q000032:analysis*
chemical_list: D009532:Nickel; D000251:Adenosine Triphosphatases; D009218:Myosins; D000252:Calcium-Transporting ATPases; D008274:Magnesium