title: Reconstitution of heavy chain and light chain 1 in cardiac subfragment-1 from hyperthyroid and euthyroid rabbit hearts.
abstract: It is now established that cardiac myosin from hyperthyroid rabbit hearts (TXM) exhibits high Ca2+ ATPase activity. The high Ca2+ ATPase activity of TXM was completely retained in cardiac myosin subfragment-1 (S-1) (1.33 +/- 0.04 mumol Pi/mg per min; euthyroid, 0.51 +/- 0.04). Cardiac S-1 from hyperthyroid and euthyroid rabbits (TXS-1 and NS-1) had the same pattern in SDS-polyacrylamide gel electrophoresis. The possible influence of heavy and light chains of TXM on increasing the ATPase activity was examined by reconstitution in the S-1 preparation. Crosswise reconstitution was performed using cardiac S-1 heavy chain (90,000 daltons) and light chain 1 (LC1) (27,000 daltons) from hyperthyroid and euthyroid hearts. Reconstitution was verified by using radiolabeled LC1. More than 95% of S-1 was recovered with full ATPase activity. When TXS-1 was reconstituted with LC1 from euthyroid hearts, the reconstituted molecule retained high ATPase activity. On the other hand, NS-1 reconstituted with LC1 from hyperthyroid hearts failed to increase the ATPase activity. The ATPase activity of S-1 was determined by the source of the heavy chain. These results suggest that the high Ca2+ ATPase activity of cardiac myosin and S-1 from hyperthyroid animals arises from the molecular alteration of the heavy chain induced by thyroxine administration.
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D000252:Calcium-Transporting ATPases / Q000032:analysis*; D004591:Electrophoresis, Polyacrylamide Gel; D006980:Hyperthyroidism / Q000378:metabolism*; D008297:Male; D008970:Molecular Weight; D009206:Myocardium / Q000032:analysis*; D009219:Myosin-Light-Chain Kinase; D010770:Phosphotransferases / Q000378:metabolism*; D011494:Protein Kinases / Q000378:metabolism*; D015800:Protozoan Proteins; D011817:Rabbits
chemical_list: D015800:Protozoan Proteins; D010770:Phosphotransferases; D011494:Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D009219:Myosin-Light-Chain Kinase; C033142:myosin-heavy-chain kinase; D000252:Calcium-Transporting ATPases