Fig. 1. A cryo-EM image of MTs decorated with dimeric ncd at subsaturating ratios reveals a cooperative binding mechanism in the axial direction, along individual protofilaments. While one of the MTs is mostly undecorated (I), partial decoration (III) and complete decoration (II) co-exist in the same area. A Fourier-filtered image of the MT and the motors in a side projection allows determination of the polarity of the MT according to the shape of the dimeric motor construct.