Electrophoretic and functional identification of two troponin C isoforms in toad skeletal muscle fibers.

The differential sensitivity of frog twitch and slow-tonic fibers to Ca(2+) and Sr(2+) suggests that these two fiber types express different troponin C (TnC) isoforms. To date, only one TnC isoform from anurans (resembling the mammalian fast-twitch isoform) has been isolated and characterized. In this study, we examined the possibility that anuran striated muscle contains more than one TnC isoform.

Troponin C isoform composition determines differences in Sr(2+)-activation characteristics between rat diaphragm fibers.

Single fibers of rat diaphragm containing different naturally occurring combinations of myofibrillar protein isoforms were used to evaluate the contribution of troponin C (TnC) isoforms to fiber type-related differences with respect to sensitivity to Sr(2+) of the contractile system. Mechanically skinned fibers were studied for their isometric force vs. Sr(2+) concentration ([Sr(2+)]) relationships and then analyzed electrophoretically for myofibrillar protein isoform composition.

Purification of troponin C isoforms from EDL and soleus muscles of the rat.

To date, there has been no report of rat TnC purification, despite the rat being an animal commonly used in physiological studies of mammalian muscle. In this study we isolated the fast and slow Troponin C isoforms from rat extensor digitorum longus (23 microg TnC/g wet weight) and soleus (17.6 microg TnC/g wet weight) muscles respectively.

A single-fibre study of the relationship between MHC and TnC isoform composition in rat skeletal muscle.

In the present study, we investigated the possibility that MHC (myosin heavy chain) and TnC (troponin C) isoforms exist in specific combinations in rat-skeletal-muscle fibres. Single fibres (numbering 245) from soleus (predominantly slow-twitch) and sternomastoid (predominantly fast-twitch) muscles of adult rats were analysed for MHC and TnC isoform composition, using alanine-SDS/PAGE for separating MHC isoforms, and a novel method (based on the previously reported influence of Ca2+ on the mobility of Ca2+-binding proteins in SDS gels) for unequivocal identification of TnC isoforms in single-fibre segments. In this study, all fibres that contained only one MHC isoform (slow or fast) contained only the matching TnC isoform and all fibres that contained multiple fast MHC isoforms contained only the fast TnC isoform.