Characterization of the Biophysical and Motility Properties of Kinesin from the Fungus Neurospora crassa(*)
- §To whom correspondence should be addressed: MCD Biology, University of Colorado, Boulder, CO 80309.
Abstract
Neurospora kinesin (Nkin) is a distant relative of the family of conventional kinesins, members of which have been identified in various
animal species. As in its animal counterparts, Nkin most likely is an organelle motor. Because it is a functional homologue
of the kinesin heavy chain of higher eukaryotes, its biophysical and motility properties were compared with those of other
conventional kinesins. Purified Nkin behaves as a homodimeric complex composed of two subunits of a 105-kDa polypeptide. Based
on its hydrodynamic properties (Stokes radius and sedimentation coefficient), Nkin is an elongated molecule, although it is
more compact than its animal counterparts. A detailed comparison of the motility properties of Nkin with those of animal conventional
kinesins reveals similarities and some intriguing differences. Nkin is less effective than other kinesins in the use of natural
nucleoside triphosphates but responds to a selection of ATP analogues in a similar fashion as mammalian kinesin. Even in the
presence of saturating concentrations of ATP, Nkin is significantly more sensitive to ADP or tripolyphosphate than other kinesins.
Both the ATP-driven microtubule gliding activity and the microtubule-stimulated ATPase activity of Nkin obey Michaelis-Menten
kinetics. Surprisingly, however, the K
values for both these activities are approximately an order of magnitude higher than those of other kinesins. Whether the
low affinity for ATP suggested by these high K
values is related to the high rate of motility remains to be determined.
Footnotes
-
↵* This work was supported by Deutsche Forschungsgemeinschaft Grant SFB 184 and a grant from the Friedrich-Baur-Stiftung. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
-
↵1 The abbreviations used are:
- Nkin
-
Neurospora kinesin
- PIPES
-
1,4-piperazinediethanesulfonic acid
- AMPPNP
-
5′-adenylyl-β,
-imidodiphosphate
- ATP
S -
adenosine 5′-O-(thiotriphosphate)
- 8-azido-ATP
-
8-azidoadenosine 5′-triphosphate
- GMPCPP
-
guanosine 5′-(α,β-methylene)triphosphate.
-
↵2G. Steinberg and M. Schliwa, unpublished results.
-
- Received September 13, 1995.
- Revision received November 30, 1995.
- © 1996 by The American Society for Biochemistry and Molecular Biology, Inc.
