I evaluated the following article for F1000 Prime.
The Microtubule-Binding Protein Ensconsin Is an Essential Cofactor of Kinesin-1.
Barlan K, Lu W, Gelfand VI.
Curr Biol 2013 PMID: 23394833 DOI: 10.1016/j.cub.2013.01.008
This paper defines the microtubule binding protein ensconsin as an obligate co-factor for kinesin-1 drive in motility in Drosophila. In a series of elegant experiments, the authors show that ensconsin is not required for the recruitment of kinesin to membranes but is in some way involved in activating the motor. Ensconsin does not seem to affect the amount of membrane-bound kinesin in cells so the authors sought to define its role in motor activation. Kinesin-1 normally exists in an auto-inhibited confirmation in cells. In a key experiment the authors showed that removal of this auto-inhibition within the kinesin-1 motor by mutation eliminates the requirement for ensoconsin in vivo. These data suggest a model in which ensconsin acts to relieve the auto-inhibition. An important point is that this function of ensconsin did not require its own microtubule binding activity. The authors postulate that spatial restriction of ensconsin to microtubules acts to refine the spatial activation of kinesin-1, adding to the diversity of mechanisms that control the spatial and temporal organization of microtubule motor activation.