Influence of nucleotide on chemical crosslinking between alkali light chains and the heavy chain of myosin subfragment 1.

When chymotryptic myosin subfragment 1 (S1) of fast skeletal muscle myosin is treated with dithiobis(succinimidylpropionate) (DSP), the alkali light chains A1 and A2 become intramolecularly crosslinked to the N-terminal 27 kDa fragment of the S1 heavy chain (Labbé et al. (1981) Biochem. Biophys. Res. Commun. 102, 466-475). The results presented here show that in the presence of MgATP the efficiency of the crosslinking is markedly reduced. The results may indicate a nucleotide-induced structural rearrangement within the myosin head. It was also observed that crosslinking depressed the nucleotide-promoted tryptic conversion of the 27 kDa fragment to its 22 kDa derivative, suggesting that the crosslinks are in the vicinity of the additional tryptic cleavage site in the 27 kDa fragment or that the crosslinking prevents nucleotide-induced conformational changes in this region of the S1 heavy chain.