X-ray Structure and Microtubule Interaction of the Motor Domain of Neurospora crassa NcKin3, a Kinesin with Unusual Processivity
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- 作者：Alexander Marx ; Jens Mü ; ller ; Eva-Maria Mandelkow ; Gü ; nther Woehlke ; Cedric Bouchet-Marquis ; Andreas Hoenger ; Eckhard Mandelkow
- 刊名：Biochemistry
- 出版年：2008
- 出版时间：February 19, 2008
- 年：2008
- 卷：47
- 期：7
- 页码：1848 - 1861
- 全文大小：1962K
- 年卷期：v.47,no.7(February 19, 2008)
- ISSN：1520-4995
文摘
Neurospora crassa kinesin NcKin3 belongs to a unique fungal-specific subgroup of smallKinesin-3-related motor proteins. One of its functions appears to be the transport of mitochondria alongmicrotubules. Here, we present the X-ray structure of a C-terminally truncated monomeric construct ofNcKin3 comprising the motor domain and the neck linker, and a 3-D image reconstruction of this motordomain bound to microtubules, by cryoelectron microscopy. The protein contains Mg·ADP bound to theactive site, yet the structure resembles an ATP-bound state. By comparison with structures of the Kinesin-3motor Kif1A in different nucleotide states (Kikkawa, M. et al. (2001) Nature (London, U.K.) 411, 439-445), the NcKin3 structure corresponds to the AMPPCP complex of Kif1A rather than the AMPPNPcomplex. NcKin3-specific differences in the coordination of the nucleotide and asymmetric interactionsbetween adjacent molecules in the crystal are discussed in the context of the unusual kinetics of thedimeric wild-type motor and the monomeric construct used for crystal structure analysis. The NcKin3motor decorates microtubules at a stoichiometry of one head per 
-tubulin heterodimer, thereby formingan axial periodicity of 8 nm. In spite of unusual extensions at the N-terminus and within flexible loopsL2, L8a, and L12 (corresponding to the K-loop of monomeric kinesins), the microtubule binding geometryis similar to that of other members of the kinesin family.
-tubulin heterodimer, thereby formingan axial periodicity of 8 nm. In spite of unusual extensions at the N-terminus and within flexible loopsL2, L8a, and L12 (corresponding to the K-loop of monomeric kinesins), the microtubule binding geometryis similar to that of other members of the kinesin family.