Crossbridge configurations

Fig. 28. Classification of crossbridge configurations in myosin filaments in different muscles. In each case, the axial separation is 143-145 A and the lateral separation is 120-150 A. There are three main classes (A) Class I, where the interaction is between heads of the same molecule as in vertebrate striated muscles (B) Class II, where interaction occurs between heads of adjacent myosin molecules in the same crown, as seen in insect (Lethocerus) flight muscles and (C) Glass III, where the interaction appears to be between heads in different crowns, as seen in tarantula and Limulus.

Al-Khayat, H. A., Hudson, L., Reedy, M. K., Irving, T. C., and Squire, J. M. (2003). Myosin head configuration in relaxed insect flight muscle X-ray modeled resting crossbridges in a pre-powerstroke state are poised for actin binding. Biophys. J. 85, 1063-1079. 

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