Abstract
Cytoplasmic dynein and kinesin are two-headed microtubule motor proteins that move in opposite directions on microtubules. It is known that kinesin steps by a ‘hand-over-hand’ mechanism, but it is unclear by which mechanism dynein steps. Because dynein has a completely different structure from that of kinesin and its head is massive, it is suspected that dynein uses multiple protofilaments of microtubules for walking. One way to test this is to ask whether dynein can step along a single protofilament. Here, we examined dynein and kinesin motility on zinc-induced tubulin sheets (zinc-sheets) which have only one protofilament available as a track for motor proteins. Single molecules of both dynein and kinesin moved at similar velocities on zinc-sheets compared to microtubules, clearly demonstrating that dynein and kinesin can walk on a single protofilament and multiple rows of parallel protofilaments are not essential for their motility. Considering the size and the motile properties of dynein, we suggest that dynein may step by an inchworm mechanism rather than a hand-over-hand mechanism.
Highlights
Cytoplasmic dynein and kinesin move on microtubules (MTs) in opposite directions and play important roles in intracellular transport and organelle positioning [1,2,3]
Gliding movements of MTs and zinc-sheets In motility experiments, we examined whether tubulin polymers exhibited gliding on a glass surface coated with cytoplasmic dynein molecules purified from porcine brain or recombinant rat kinesin1 dimers fused with an Avi-tag (RK430-Avi) (Fig. S2)
Zinc-macrotubes bound to the dyneinand kinesin-coated surfaces, but did not show gliding movement. These results indicate that protofilament arrangements on the zinc-macrotube surface cannot support dynein and kinesin movement
Summary
Cytoplasmic dynein and kinesin move on microtubules (MTs) in opposite directions and play important roles in intracellular transport and organelle positioning [1,2,3]. Dysfunction of these proteins can lead to serious diseases and death [4,5]. Dynein occasionally takes off-axis steps on MTs [20,22], whereas kinesin walks along the MT longitudinal axis or follows the protofilament path with high fidelity [23,24]. The minimum number of protofilaments required for supporting dynein and kinesin movement is unknown
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