Structural snapshots of the kinesin‐2 OSM‐3 along its nucleotide cycle: implications for the ATP hydrolysis mechanism

Motile kinesins are motor proteins that translocate along microtubules as they hydrolyze ATP. They share a conserved motor domain which harbors both ATPase and microtubule‐binding activities. An ATP hydrolysis mechanism involving two water molecules has been proposed based on the structure of the kinesin‐5 Eg5 bound to an ATP analog. Whether this mechanism is general in the kinesin superfamily remains uncertain. Here, we present structural snapshots of the motor domain of OSM‐3 along its nucleotide cycle. OSM‐3 belongs to the homodimeric kinesin‐2 subfamily and is the Caenorhabditis elegans homologue of human KIF17. OSM‐3 bound to ADP or devoid of a nucleotide shows features of ADP‐kinesins with a docked neck linker. When bound to an ATP analog, OSM‐3 adopts a conformation similar to those of several ATP‐like kinesins, either isolated or bound to tubulin. Moreover, the OSM‐3 nucleotide‐binding site is virtually identical to that of ATP‐like Eg5, demonstrating a shared ATPase mechanism. Therefore, our data extend to kinesin‐2 the two‐water ATP hydrolysis mechanism and further suggest that it is universal within the kinesin superfamily. PROTEIN DATABASE ENTRIES: 7A3Z, 7A40, 7A5E.