Thermal denaturation of the alkali light chain-20 kDa fragment complex obtained from myosin subfragment 1

The thermal denaturation of the myosin subfragment 1 (S1) from rabbit skeletal muscle and of its derivatives obtained by tryptic digestion has been studied by means of differential scanning calorimetry. Two distinct thermal transitions were revealed in the isolated complex of the C-terminal 20 kDa fragment of the S1 heavy chain with the alkali light chain. These transitions were identified by means of a thermal gel analysis method. It has been shown that the thermal denaturation of the 20 kDa fragment of the S1 heavy chain correlates with the melting of the most thermostable domain in the S1 molecule. It is concluded that this domain is located in the C-terminal 20 kDa segment of the S1 heavy chain.