Fig. 2.

Kinesin structure and motility. (A) General schematic of a dimeric kinesin motor protein showing the motor, stalk and tail domains. (B) Processive motility of a truncated (constitutively active) kinesin along the microtubule surface. Alternating ATP hydrolysis by the two motor domains enables stepping (movement from one tubulin subunit to the next) along a protofilament of a microtubule. In the absence of nucleotide or in the presence of the non-hydrolyzable analog AMPPNP, kinesins bind statically to the microtubule surface. T, ATP; D, ADP; N, AMPPNP; −, no nucleotide.