Figure 2.

Roles of the neck linker domain in kinesin stepping. When both heads are bound, the entropic elasticity of the neck linkers mediates interhead tension. Rear-head gating is defined as the accelerated detachment of the rear head due to this interhead tension. In the 1HB state, neck linker docking in the bound head causes a forward displacement of the tethered head. Following docking, entropic elasticity in the neck linker of the tethered head constrains its diffusional search for the next binding site. At right is a plot showing the nonlinear elasticity of a 14 or 17 amino acid polypeptide modeled as a WLC with 0.7 nm persistence length, showing different predicted forces at an extension of 4 nm, the distance needed to span the tubulin interdimer distance (16, 21). To see this figure in color, go online.