Skating on MTs

Dynactin can skate along the length of a microtubule (MT), giving a boost to the attached dynein motor's forward progress, according to Tara Culver-Hanlon, Stephen King (University of Missouri, Kansas City, MO), and colleagues.

Dynein is a poorly processive motor compared with others like kinesin. “It doesn't stay on the microtubule worth a hoot,” says King. To be efficient, dynein needs dynactin, which has its own MT-binding domains. King's group found that dynactin had not only the well-known CAP-Gly MT-binding domain, but also a neighboring basic domain that bound MTs.

When the group attached the domains to beads for single-particle tracking along MTs, the beads moved in distinctly different ways. CAP-Gly beads missing the basic sequence only swiveled around a relatively fixed point on the MT. Beads with only the basic domain or...