Kinesin Superfamily Proteins

Abstract

Kinesin was first identified biochemically as a microtubule-dependent motor protein responsible for transport of membranous organelles in the axon. It is now recognized that microtubule-dependent motor proteins form a large gene family, kinesin superfamily proteins (KIFs). The human genome contains 45 KIF genes. KIFs have high homology at the so-called ‘motor domain’, which is a globular domain responsible for moving along microtubules by hydrolysis of adenosine triphosphate (ATP). Outside the motor domain, the sequence is unique to each member. The motors bind to the ‘cargoes’, the molecule to be transported, at this domain. KIFs transport many different types of cargoes including membranous organelles, protein complexes, and messenger RNAs (mRNAs). They play important roles in a wide variety of intracellular transport, such as transport from Golgi to plasma membrane pathways involved in exocytosis and endocytosis, axonal transport, transport in dendrites, and special transport called intraflagellar transport. In addition, recent molecular genetic experiments have uncovered unexpected roles for KIFs in the regulation of such physiologic processes as higher brain function, tumour suppression, and developmental patterning. They also play important roles in mitosis. Functions and/or dysfunctions of KIF motors underlie some diseases. The molecular mechanisms by which different KIFs recognize and bind to specific cargoes, and how their binding is regulated, have been identified for some KIFs.