Commentary Leading the Procession: New Insights into Kinesin Motors

he view that proteins are, in essence, nanoscale macromolecular machines is helping to foster a new paradigm in biology, with an interdisciplinary em-phasis that incorporates strong elements of biophysics (1). Remarkable examples of cellular machinery abound, in-cluding ribosomes, polymerases, proteosomes, chapero-nins, and spliceosomes. But perhaps no more spectacular example of proteins-as-machines exists than the motor proteins, also called mechanoenzymes. These molecular assemblies drive both rotary and linear motions in virtu-ally all organisms. Rotary engines include the F