Thermal unfolding of homodimers and heterodimers of different skeletal-muscle isoforms of tropomyosin

We applied differential scanning calorimetry (DSC) to investigate the structural properties of three isoforms of tropomyosin (Tpm), alpha, beta, and gamma, expressed from different genes in human skeletal muscles. We compared specific features of the thermal unfolding of alpha alpha, beta beta, and gamma gamma Tpm homodimers, as well as of alpha beta and gamma beta Tpm heterodimers. The results show that the thermal stability of gamma gamma homodimer is much higher than that of alpha alpha homodimer which, in turn, is much more thermostable than the beta beta homodimer. The stability of the gamma beta Tpm heterodimer is much lower than that of the gamma gamma homodimer, and its thermal unfolding is quite different from that for gamma gamma and beta beta homodimers, whereas the unfolding of the alpha beta heterodimer is roughly similar to that of the alpha alpha homodimer.