title: The isolation and characterization of the ATPase inhibitory protein (TN-I) from bovine cardiac muscle.
abstract: The inhibitory component of the troponin complex (TN-I) was purified from bovine cardiac muscle, using a combination of ion exchange and molecular exclusion chromatographies in the presence of urea. It has the ability to inhibit the Mg2+-activated APTase (EC 3.6.1.3) of a synthetic cardiac actomyosin preparation and this inhibition is reversed by the addition of cardiac calcium binding component of troponin (TN-C). Conventional sedimentation equilibrium experiments suggest a molecular weight for cardiac TN-I of 22 900 +/- 500. However, sodium dodecyl sulfate (SDS) gels indicate a molecular weight of 27 000 +/- 1000. The mobility of TN-I on SDS gels may be anomalous due to the high proportion of basic amino acid residues in the protein. Cardiac TN-I and TN-C interact to form a tight complex, even in the presence of 6 M urea. The results of this study invite direct comparison with results published for rabbit skeletal TN-I.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000596:Amino Acids / Q000032:analysis; D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000302:isolation & purification; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D009124:Muscle Proteins / Q000302:isolation & purification*; D009206:Myocardium / Q000201:enzymology*; D011487:Protein Conformation; D013056:Spectrophotometry, Ultraviolet; D014336:Troponin / Q000302:isolation & purification* / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D004791:Enzyme Inhibitors; D009124:Muscle Proteins; D014336:Troponin; D000251:Adenosine Triphosphatases; D008274:Magnesium