Introduction to Muscle Contraction, Part 2

This state could be influenced by the missing light chains

Since the experiments on dictyostelium myosin have used a truncated form, Smith and Rayment have urged caution in interpreting the results incase they should be caused in some way by the absense of the light chains or effects of crystal packing. In addition, the converter domain is partly disordered. Infact, the model building shows no conflict between the essential light chain and the N-terminal part of the myosin heavy chain. Moreover, a sequence comparison between 80 different myosin sequences (Cope et al, 1996) shows that there is a core myosin sequence which terminates exactly at the point where Smith and Rayments truncation occured. Beyond this point myosin sequences vary according to the number and type of light chains bound. Therefore, it would appear that there is a good chance that the results with bound ADP vanadate are to be taken at their face value. Moreover, an independent determination of the ADP.BeFxstructure (see below) shows very similar effects to those found with ADP.vanadate although the crystal packing is quite different.

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