Figure 2.

Individual kinesin motors immobilized on MTs in the presence of 15 μM AMP-PNP. Both images are 3D-rendered. (A) Intermediate kinesin concentration (<1 motor/tubulin dimer). Individual motors could be clearly distinguished. Heads always appeared in pairs, aligned parallel to the MT axis. (B) Low kinesin concentration (<1 motor/10 tubulin dimers). Isolated motors could be seen. Both heads were bound to the same protofilament. (Upper inset) Averaged axial profile of 17 kinesin molecules, interhead spacing: 8 nm, height: 3.0 nm. (Lower inset) Laplacian filtered image of another kinesin molecule showing clearly the two heads and a ∼10 nm long structure that might represent the stalk.