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Motor Protein — Kinesin Walking
Hand-over-hand stepping of kinesin along a microtubule. Each ATP hydrolysis drives an 8 nm step. Cargo transported; force-velocity curve; tug-of-war.
Kinesin is a dimeric motor that walks hand-over-hand along microtubules toward the plus end. Each step is exactly 8 nm (one tubulin dimer). The mechanism: one head is bound, the unbound head swings forward (powered by ATP hydrolysis ~50 nm "power stroke"), lands on the next tubulin, releases the rear head. Stall force ≈ 6–7 pN. The force-velocity relationship (Svoboda & Block 1994) is approximately linear until stall. Multiple motors cooperate to carry larger loads; dynein teams tug toward the minus end (tug-of-war model).