Proximity and ligand-induced movement of interdomain residues in myosin subfragment 1 containing trapped MgADP and MgPPi probed by multifunctional cross-linking.

摘要: The conformations of myosin subfragment 1 containing trapped MgADP or MgPPi have been studied by investigating the spatial disposition remainder structure to covalently bridged ATPase-related thiols SH1 and SH2. This has done synthesizing a trifunctional photoactivatable reagent 4,4'-bis(N-maleimido)benzophenone reacting it with in presence these ligands. Modification this mimics closely changes ATPase properties as noted previously for modification p-phenylenedimaleimide. In addition, noncovalent trapping nucleotide also results, presumably bridging SH2 thiols. On photolysis, cross-linking from other regions can be observed, but extent course photoinduced depend on nature ligand. For MgADP, high efficiency occurs between 21-kDa segment 50-kDa segment. With ligand, low either 27-kDa N-terminal segments heavy chain. These results indicate that without adenosine moiety, binding leaves protein flexible state so residues both move within span activated benzophenone triplet. apparently more rigid which are spatially close thiols, thus enabling photocross-linking proceed higher efficiency.