3D electron microscopy of the interaction of kinesin with tubulin

We have studied the structure of microtubules decorated with kinesin motor domains in different nucleotide states by 3D electron microscopy. Having do cked the atomic coordinates of both dimeric ADP.kinesin and tubulin heterod imer into a map of kinesin dimers bound to microtubules in the presence of ADP, we try to predict which regions of the proteins interact in the weakly binding state. When either the presence of 5'-adenylyimidodiphosphate (AMP -PNP) or an absence of nucleotides puts motor domains into a strongly-bound state, the 3D maps show changes in the motor domains which modify their in teraction with beta-tubulin. The maps also show differences in beta-tubulin conformation compared with undecorated microtubules or those decorated wit h weakly-bound motors. Strongly-bound ncd appears to produce an identical c hange.