Fig. 1. Structural comparison of kinesin and myosin. (A) Front view of kinesin (rat monomeric KHC, PDB 2KIN) (Sack et al., 1997) and myosin II (scallop S1-ADP·VO₄, PDB 1DFL) (Houdusse et al., 2000). Core ß-strands with adjacent nucleotide-binding (P-loop) or switch regions are colored green (P-loop), purple (switch I) and cyan (switch II). The helix following switch II, the ‘relay’ helix, is red in the two motors. Other ß-strands and -helices common to kinesin and myosin are shown in dark blue-gray and unique areas are in light gray. The myosin converter and kinesin neck helix and neck linker are shown in pink-purple. The myosin lever arm is tan. (B) Back view, rotated 180° from the view in A, showing the filament-binding face of the motors. Switch II at the active site of myosin is connected to the relay helix, which interacts with the converter and lever arm at its other end - the converter can therefore convert changes at the active site into movements of the lever arm.

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