In a new study, which appears in the Feb. 5 issue of Nature, researchers based at Hannover Medical School and the Max Planck Institute for Medical Research in Germany describe the engineering of an artificial backwards-moving myosin from three pre-existing molecular building blocks. These blocks are: a forward-moving class-I myosin motor domain, a directional inverter formed by a four-helix bundle segment of human guanylate-binding protein-1 and an artificial lever arm formed by two alpha-actinin repeats. Drs Tsiavaliaris, Fujita-Becker and Manstein's results demonstrate that reverse-direction movement of myosins can be achieved simply by rotating the direction of the lever arm 180.

Myosins are mechano-enzymes that contain a common motor domain, by which they convert the energy from the hydrolysis of adenosine triphosphate into movement exerted against polar actin filaments. On the basis of sequence comparisons the myosin superfamily can be divided into at least 18 classes. Most myosins move towards the "barbed" end of actin filaments, but recent studies have established that at least one member of the family, myosin VI, moves towards the "pointed" end.

"The results lend support to a model that suggests that myosins and microtubule-based molecular motors of the kinesin family, which share a common fold consisting of seven beta-strands and six alpha-helices, are intrinsically plus-end directed motors. Conformational changes in the core motor domain are either amplified or amplified and redirected by the neck region in both protein classes," note the researchers.

"The work is based on a very simple idea namely that the translational movement of the tip of a lever depends on the angle of rotation and the direction in which the lever projects away from the axis of rotation. The difficult part was to rotate the direction of the lever arm in precisely the right orientation without creating sterical clashes between domains and compromisin
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Contact: Prof. Dietmar J. Manstein
manstein@bpc.mh-hannover.de
0049-511-532-3700
Max-Planck-Gesellschaft
6-Feb-2004

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