MICROTUBULE-BASED ATPases of the kinesin superfamily1,2 provide the motile force for many animated features of living cells. Kinesin motors differ in their direction of movement along microtubules. Kinesin3 and ncd4,5, a kinesin-related motor involved in formation and maintenance of mitotic and meiotic spindles, move in opposite directions along microtubules, even though their motor domains are 40% identical in amino-acid sequence. Here we report the crystal structure of the MgADP complex of the Drosophila ncd motor domaindetermined to 2.5 Å by X-ray crystallography, and compare it to the kinesin structure. The ncd and kinesin motor domains are remarkably similar in structure, and the locations of conserved surface amino acids suggest these motors share a common microtubule-binding site. Moreover, structural and functional comparisons of ncd, kinesin, myosin and G proteins indicate that these NTPases may have a similar strategy of changing conformation between NTP and NDP states. We propose a general model for converting a common γ-phosphate-sensing mechanism into opposite polarities of movementfor kinesin and ncd.

Molecular motors move directionally to either the plus or the minus endof microtubules or actin filaments. Kinesin moves towards microtubule plusends, whereas the kinesin-related Ncd motor moves to the minus ends. The ‘neck’—theregion between the stalk and motor domain—is required for Ncd... mehr

KINESIN is the founding member of a superfamily of microtubule-based motor proteins that perform force-generating tasks such as organelle transport and chromosome segregation1,2. It has two identical ∼960-amino-acid chains containing an ammo-terminal globular motor domain, a central α-helical... mehr

To understand the mechanism of kinesin movement we have investigated the relative configuration of the two kinesin motor domains during ATP hydrolysis using fluorescence polarization microscopy of ensemble and single molecules. We found that: (i) in nucleotide states that induce strong... mehr