Fig. 4.

Asymmetric motor competition model (AMCM). A sequence of events for tug-of-war-mediated plus → minus and minus → plus reversals is schematized. A single kinesin is shown in a tug-of-war against six dyneins. Note endosome stretching in the minus direction in both cases, with the kinesin-attached plus end being almost stationary. One dynein exerts ≈1.1 pN force, whereas kinesin exerts ≈5.5 pN. Dynein is also more prone to detachment than kinesin under applied backward force (load). These asymmetries in number and single-motor properties combine to ensure net minus transport of endosomes with occasional reversals and fission (see main text).