Figure 6: A model for dynein motility.

(a) Two proposed mechanisms of dynein stepping. (Left) when the heads are close to each other, either head can release the MT and step forward upon ATP binding. (Right) When the heads are far apart, tension on the linker prevents ATP-dependent MT release, and the asymmetry of the release rates under tension favors the trailing head to take a step. (b) A representative Monte Carlo simulation of dynein motility shows stepping of the two head domains (blue and red). (c) The trailing head is more likely to take a step in simulated traces as the interhead separation increases. The data shown are the average of 200 simulations (±s.d.). (d) The average velocity of 200 100-s simulated traces (±s.e.m.) agrees well with measured velocities for various dynein mutants (±s.e.m., n>100). The results of the model are within ±15% of the experimental data.