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. Author manuscript; available in PMC: 2006 Aug 15.
Published in final edited form as: Biochemistry. 2004 Mar 16;43(10):2792–2803. doi: 10.1021/bi035830e

FIGURE 1.

FIGURE 1

Alternating site model for kinesin stepping. The cycle begins as head 1 binds the microtubule with rapid ADP release. ATP binding at head 1 leads to the plus-end-directed motion of the neck linker to position head 2 forward at the next microtubule binding site. ATP binding at head 1 is sufficient to promote head 2 association with the microtubule followed by rapid ADP release. ATP hydrolysis at head 1 promotes tight binding of head 2 onto the microtubule, resulting in an intermediate with both heads strongly bound to the microtubule and with the neck linkers under mechanical strain. Phosphate is released, and the rearward head detaches from the microtubule. The active site of head 2 is now accessible for ATP binding, and the cycle is repeated.