Motor proteins of the kinesin superfamily: structure and mechanism.

Kinesins are ATP-driven microtubule motor proteins that produce directed force. The kinesin superfamily currently encompasses over 100 eukaryotic proteins containing a common motor domain. Both the nucleotide-binding fold and active-site chemistry of the motor domain are also present in the actin-based motor, myosin. Kinesins can be classified into three groups based on the position of their motor domains: N-terminal, C-terminal and internal kinesins. Conventional kinesin operates as a dimer, walking in a co-ordinated, hand-over-hand fashion along a microtubule protofilament. X-ray crystal structures and EM reconstructions show major differences in the quaternary arrangement of kinesin domains in minus-end- and plus-end-directed motors. Kinesin's neck region, directly adjacent to the motor domain, dictates directionality.