Insulin keeps time

VASP comet sightings ess is more when it comes to actin-fueled propulsion. Julie Plastino, Stéphane Olivier, and Cécile Sykes (Institut Curie, Paris, France) show that hollow actin comets propel beads faster than a more filament-packed comet. Actin comets, which drive bead or bacteria movement, are thought to depend strongly on Arp2/3–built, branched actin networks. Now, Plastino et al. show that another actin polymerizer, VASP, builds comet tails that are less dense overall and hollow in the center, but nevertheless led to bead speeds that were seven times that of Arp2/3– built tails. “It’s not about having as much polymer as possible,” says Plastino. “It’s how the geometry of filaments affects movement.” VASP is thought to weaken interactions between actin filaments and the membrane or bead. The first filaments to be detached would be those at the center back of the bead, as these beadfilament attachments produce the strongest pullL