title: Hydrodynamic properties of bovine cardiac troponin C.
abstract: The size and shape of bovine cardiac troponin C (TN-C) in solution have been examined by gel filtration, ultracentrifugation, and viscosity in the presence and absence of Ca2+. Cardiac TN-C (-Ca2+) has an intrinsic sedimentation coefficient, s020,w, of 1.87 S and a Stokes radius, RS, of 26.3 A as determined by gel chromatography on Sephacryl S-300. In 2 mM Ca2+, S020,w is increased to 2.04 S and RS is decreased to 24.3 A, indicating a conformational change to a more compact structure. Furthermore, the intrinsic viscosity of TN-C in the absence of Ca2+ (6.4 mL/g) is reduced to 5.4 mL/g when Ca2+ is added. Sedimentation equilibrium studies indicate that the effects of Ca2+ are not due to changes in the molecular weight of the protein. The hydrodynamic data suggest that TN-C is a moderately asymmetric protein with an axial ratio of 4--6.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002850:Chromatography, Gel; D009124:Muscle Proteins / Q000378:metabolism; D009206:Myocardium / Q000648:ultrastructure*; D011485:Protein Binding; D011487:Protein Conformation; D014336:Troponin / Q000378:metabolism; D019209:Troponin C; D014461:Ultracentrifugation
chemical_list: D009124:Muscle Proteins; D014336:Troponin; D019209:Troponin C; D002118:Calcium