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), α, β, and γ, expressed from different genes in human skeletal muscles. We compared specific features of the thermal unfolding of αα, ββ, and γγ Tpm homodimers, as well as of αβ and γβ Tpm heterodimers. The results show that the thermal stability of γγ homodimer is much higher than that of αα homodimer which, in turn, is much more thermostable than the ββ homodimer. The stability of the γβ Tpm heterodimer is much lower than that of the γγ homodimer, and its thermal unfolding is quite different from that for γγ and ββ homodimers, whereas the unfolding of the αβ heterodimer is roughly similar to that of the αα homodimer.