Motors take turns

T wo opposing microtubule motors are wary of competition, say Comert Kural, Paul Selvin (University of Illinois, Urbana, IL), Vladimir Gelfand (Northwestern University, Chicago, IL), and colleagues. Rather than play tug-of-war, dynein and kinesin take turns carting around their cargo—in this case, peroxisomes.

Kinesin takes peroxisomes out to the cell periphery, whereas dynein brings them back to the interior. No matter which direction ultimately prevails, the peroxisome switches direction many times along the way. These switches might stem from the alternation of active motors or from a tug-of-war with alternating short-term winners. To distinguish between these possibilities, the authors visualized peroxisome movement at high resolution in vivo. The results suggest that either dynein or kinesin, but not both, pulls at any given time.

The high resolution...