Polymorphic forms of troponin T and troponin C and their localization in striated muscle cell types

Abstract

1. 1. Immunochemical studies have shown that the major forms of troponin T present in fast skeletal, slow skeletal and cardiac muscles are different proteins. 2. 2. Similar studies indicate that the major form of troponin C present in fast skeletal muscles differs from troponin C present in slow skeletal and cardiac muscle cells. The forms of troponin C present in slow skeletal and cardiac muscles are immunochemically very similar. 3. 3. The antibodies to the polymorphic forms of troponin T and troponin C are specific for the muscle type, except in the case of the slow skeletal and cardiac muscle forms of troponin C. 4. 4. By the immunoperoxidase technique, it has been shown that the fast skeletal muscle troponin T is localized in type II cells and slow skeletal muscle troponin T in type I cells. 5. 5. Fast skeletal muscle troponin C is present in type II cells and a different troponin C, identified by its reaction with the antibody against cardiac troponin C, is present in type I cells. 6. 6. It is concluded that in normal adult skeletal muscle, fast muscle forms of troponin I, troponin T and troponin C are present together as a homocomplex in type II cells and the slow muscle forms exist as an analagous homocomplex in type I cells.