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Force analysis shows the formation of the cover neck bundle (yellow) is at the heart of kinesin's power stroke. HWANG/ELSEVIER

Kinesin creates a new domain to generate its power, according to Wonmuk Hwang (Texas A&M University, College Station, TX), Matthew Lang (Massachusetts Institute of Technology, Cambridge, MA), and Martin Karplus (Harvard University, Cambridge, MA).

Kinesin's structure includes a cargo-binding domain, a long stalk, and a pair of motor heads, which move along microtubules mostly hand over hand. Each motor head is connected to the stalk by a short neck linker. The neck linker has been suggested to help kinesin motility by making a large, ATP-driven conformational change that docks it to the motor head and results in a forward-stepping motion. But an unbound neck linker is flexible and interacts only weakly with the motor head; thus, it alone cannot generate the required force. The authors now discover an additional mechanical element not previously implicated in kinesin motility—the cover strand, which dangles nearby.

When ATP binds to the motor head, the cover strand and the neck linker form a new β-sheet domain, which the authors named the cover neck bundle. The bundle pushes the neck linker into its binding pocket, where it then latches on, powering the free motor head forward. Force analysis indicated that forces generated by the cover neck bundle agreed with experimental measurements.

"The force is generated by the formation of this domain rather than by switching between well-defined conformations," Hwang says. "It was not possible to obtain these results from structural studies only, since it's a dynamic structure."

Reference:

Hwang, W., et al. 2008. Structure. 16:62–71.[Medline]

Richard Robinson

rrobinson{at}nasw.org

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This Article PDF (Full Text) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Robinson, R. Search for Related Content PubMed Articles by Robinson, R. Social Bookmarking                      What's this?