MOTOR PROTEINS:- HOW DOES KINESIN MOVE ALONG MICROTUBULES?

Isabelle Arnal and Richard H. Wade
Institut de Biologie Structurale (CEA & CNRS), 41 Avenue des Martyrs, 38027 Grenoble Cedex 1, France

Compared to myosin and dynein, kinesin provides a simple model for understanding molecular motors. The kinesin superfamily of motor proteins use ATP hydrolysis to move along microtubules and they play crucial roles in eucaryotic cells. Most of these motors are heterotetramers with two heavy and two light chains. Each heavy chain has a globular motor domain that binds ATP and interacts with microtubules and shows a high degree of sequence homology throughout the family. We have used electron cryomicroscopy and three dimensional reconstruction methods to determine the conformation of functional kinesin motors interacting with microtubules. Three-dimensional maps obtained at different stages in the ATP hydrolysis cycle (imitated by microtubule/kinesin complexes prepared in the presence of AMP-PNP, ADP-AlF4, ADP and apyrase) show significant conformational changes of the kinesin dimer, giving some structural clues as to how kinesin moves along microtubules.