Soppina V, Verhey KJ. The family-specific K-loop influences the microtubule on-rate but not the superprocessivity of kinesin-3 motors.
Mol Biol Cell 2014;
25:2161-70. [PMID:
24850887 PMCID:
PMC4091829 DOI:
10.1091/mbc.e14-01-0696]
[Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The kinesin-3 family–specific, positively charged insert, the K-loop, in loop 12 of the motor domain plays a critical role in cargo transport by enhancing the initial interaction of cargo-bound dimeric motors with the microtubule. The replacement of the K-loop, however, does not abolish the superprocessive motion of this class of kinesin motors.
The kinesin-3 family (KIF) is one of the largest among the kinesin superfamily and an important driver of a variety of cellular transport events. Whereas all kinesins contain the highly conserved kinesin motor domain, different families have evolved unique motor features that enable different mechanical and functional outputs. A defining feature of kinesin-3 motors is the presence of a positively charged insert, the K-loop, in loop 12 of their motor domains. However, the mechanical and functional output of the K-loop with respect to processive motility of dimeric kinesin-3 motors is unknown. We find that, surprisingly, the K-loop plays no role in generating the superprocessive motion of dimeric kinesin-3 motors (KIF1, KIF13, and KIF16). Instead, we find that the K-loop provides kinesin-3 motors with a high microtubule affinity in the motor's ADP-bound state, a state that for other kinesins binds only weakly to the microtubule surface. A high microtubule affinity results in a high landing rate of processive kinesin-3 motors on the microtubule surface. We propose that the family-specific K-loop contributes to efficient kinesin-3 cargo transport by enhancing the initial interaction of dimeric motors with the microtubule track.
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