Kinectin-kinesin binding domains and their effects on organelle motility.

Intracellular organelle motility involves motor proteins that move along microtubules or actin filaments. One of these motor proteins, kinesin, was proposed to bind to kinectin on membrane organelles during movement. Whether kinectin is the kinesin receptor on organelles with a role in organelle motility has been controversial. We have characterized the sites of interaction between human kinectin and conventional kinesin using in vivo and in vitro assays. The kinectin-binding domain on the kinesin tail partially overlaps its head-binding domain and the myosin-Va binding domain. The kinesin-binding domain on kinectin resides near the COOH terminus and enhances the microtubule-stimulated kinesin-ATPase activity, and the overexpression of the kinectin-kinesin binding domains inhibited kinesin-dependent organelle motility in vivo. These data, when combined with other studies, suggest a role for kinectin in organelle motility.