Drivers and passengers wanted! The role of kinesin-associated proteins

Members of the kinesin superfamily of proteins participate in a wide variet y of cellular processes. Although much attention has been devoted to the st ructural and biophysical properties of the force-generating motor domain of kinesins, the factors controlling the functional specificity of each kines in have only recently been examined. Genetic and biochemical approaches hav e identified two classes of proteins that associate physically with the div erse non-motor domains of kinesins. These proteins can be divided into two general classes: first, those that form tight complexes with the kinesin an d are instrumental in directing the distinct function of the motor (i.e. dr ivers) and, second, those proteins that might transiently interact with the motor or be an integral part of the motor's cargo (i.e. passengers). Here, we discuss known kinesin-binding proteins, and how they might participate in the activity of their motor partners.