The Length of the Neck Linker Domain Controls Processivity Across Diverse N-Terminal Kinesin Families

Abstract

Consistent with their diverse intracellular roles, the processivity of N-terminal kinesin motors varies considerably between different families. Gating mechanisms that control kinesin processivity involve inter-head tension that must be transmitted through the neck linker domains of each head. The objective of this study is to determine the degree to which unloaded processivity is controlled by the length of the neck linker, as opposed to kinetic differences in the core motor domains. The motor and neck linker domains of Kinesin-2, 3, 5 and 7 were fused to the neck-coil and rod domains of Kinesin-1 and run lengths of GFP-tagged motors visualized by total internal fluorescence microscopy. When the neck linkers were shortened to the 14 amino acids found in Kinesin-1, all motors had similar run lengths, and when the neck linkers were extended the run lengths fell. These results suggest that inter-head tension, which is regulated by the mechanical properties of the neck linker, controls processivity in a conserved manner across diverse kinesins. Monte Carlo modeling of the kinesin hydrolysis cycle conclude that the results can be quantitatively accounted for by differences in either front head or rear head gating.