Intrinsic Disorder in the Kinesin Superfamily.

Kinesin molecular motors perform a myriad of intracellular transport functions. While their mechanochemical mechanisms are well understood and well-conserved throughout the superfamily, the cargo-binding and regulatory mechanisms governing the activity of kinesins are highly diverse and in general, are incompletely characterized. Here we present evidence from bioinformatic predictions indicating that most kinesin superfamily members contain significant regions of intrinsically disordered (ID) residues. ID regions can bind to multiple partners with high specificity, and are highly labile to post-translational modification and degradation signals. In kinesins, the predicted ID regions are primarily found in areas outside the motor domains, where primary sequences diverge by family, suggesting that ID may be a critical structural element for determining the functional specificity of individual kinesins. To support this idea, we present a systematic analysis of the kinesin superfamily, family by family, for predicted regions of ID. We combine this analysis with a comprehensive review of kinesin binding partners and post-translational modifications. We find two key trends across the entire kinesin superfamily. First, ID residues tend to be in the tail regions of kinesins, opposite the superfamily-conserved motor domains. Second, predicted ID regions correlate to regions that are known to bind to cargoes and/or undergo post-translational modifications. We therefore propose that ID is a structural element utilized by the kinesin superfamily in order to impart functional specificity to individual kinesins.