We choose the kinesins to illustrate similarities and differences between protein family databases. Kinesin and its relatives are motor proteins that utilize ATP hydrolysis to move along microtubules in eukaryotic cells. The motor portion of a kinesin is structurally very similar to that of the myosin motor, which moves along actin filaments, although no sequence similarity is evident between them. This is an example of likely divergence from an ancestral fold that is beyond current sequence- based comparison methods to detect. Kinesin subfamilies based on sequence similarities betweenmotor domains are strongly predictive of cellular function, indicating diver- gence from an ancestral kinesin-like motor. Kinesins are multidomain proteins, with a coiled-coil stalk attached to the.
