Bovine cardiac troponin subunits: binary complexes and reconstitution of whole troponin

The reconstitution of bovine cardiac troponin from its subunits has been investigated using hydrodynamic techniques. Gel filtration (Sephacryl S-300) and sedimentation velocity experiments indicate that troponin-C and troponin-I form a stable binary complex (1:1 mole ratio) with an apparent Stokes' radius of 36 A (frictional ratio = 1.6). Troponin-C and troponin-T do not interact significantly while troponin-I and troponin-T undergo partial complex formation. The effect of subunit ratio on the reconstitution of whole troponin has been examined by SDS-polyacrylamide gel electrophoresis and gel filtration and the results suggest that native troponin contains the subunits in an equimolar ratio.