PUBLIC INFORMATION FOR:

C.L. Asbury, A.N. Fehr, and S.M. Block (2003) (Full Text PDF)
Science Dec 19 2003: 2130-2134.

Kinesin Moves by an Asymmetric Hand-Over-Hand Mechanism

Click here for the press release


Summary

Kinesin is a double-headed motor protein that moves along microtubules in 8-nm steps. Two broad
classes of model have been invoked to explain kinesin movement: hand-over-hand and inchworm.
In hand-over-hand models, the heads exchange leading and trailing roles with every step, whereas no
such exchange is postulated for inchworm models, where one head always leads. By measuring the stepwise
motion of individual enzymes, we find that some kinesin molecules exhibit a striking alternation in the
dwell times between sequential steps, causing these motors to "limp" along the microtubule. Limping
implies that kinesin molecules strictly alternate between two different conformations as they step,
indicative of an asymmetric, hand-over-hand mechanism.

Images and Movies

ALL IMAGES ARE COPYRIGHTED AND MAY BE USED WITH PERMISSION.
CONTACT: Prof. Steven Block sblock@stanford.edu


1. Structure cartoon (Credit: C. Asbury)


[StructureCartoon.jpg 172 KB]


2. Kinesin constructs (Credit: C. Asbury)


[motormaps.jpg 205 KB]


3. Kinesin walks hand-over-hand (Credit: C. Asbury)



[KinesinWalking.jpg 155 KB]


4. Limping of truncated fly kinesin, DmK401 (Credit: C. Asbury)


[LimpingTrace.jpg 303 KB]


5. Kinesin-driven bead movement along a microtubule (Credit: J. Shaevitz)


[FreeMover.avi 741 KB]


6. Kinesin movement against an optical trap (Credit: J. Shaevitz)


[TrappedBead.avi 1311 KB]




Steven M. Block
Prof. of Applied Physics & Biological Sciences
Stanford University
Phone: 650-724-4046
Email: sblock@stanford.edu