Cloning and functional expression of a 'fast' fungal kinesin.

Conventional kinesins are molecular motors that move towards the plus end of microtubules. In animal species, they have been shown to be remarkably conserved in terms of both their primary sequence and several physiological properties, including their velocity of movement. Here we report the cloning of Synkin, a homologue of conventional kinesin from the zygomycete fungus Syncephalastrum racemosum [Steinberg, Eur. J. Cell Biol. 73 (1997) 124-131] that is 4-5 times faster than its animal counterparts. Expression in bacteria yields a fully functional motor that moves at the same speed as the native motor isolated from fungal hyphae and has similar hydrodynamic properties. Its sequence is most closely related to that of two other fungal kinesins from Neurospora and Ustilago, and shares several biochemical properties with the Neurospora motor. Fungal kinesins therefore seem to form a conserved subfamily of conventional kinesins distantly related to animal kinesins. They may help to identify sequence features important for determining motor velocity.