Worm Breeder's Gazette 9(3): 118

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Identification of a Microtubule-Based Cytoplasmic Motor in the Nematode C. elegans

R.J. Lye, M.E. Porter, J.M. Scholey and J.R. McIntosh

We have identified a protein in C. bines 
properties of the flagellar ATPase, dynein with those of the 
microtubule-dependent translocator, kinesin. The microtubule 
stabilizing drug, taxol, has been used to drive microtubule assembly 
in extracts of either gravid adult worms or of embryos, and the 
resulting polymers have been isolated by differential centrifugation. 
One of the microtubule-associated proteins (Mr. approx. 400K) can be 
extracted from the polymer by 10 mM ATP and 100 mM NaCl. This 
polypeptide and a Mg-ATPase activity cosediment on sucrose density 
gradients at approximately 20 S. The specific activity of the peak 
fraction is 60 - 120 nanomoles ATP hydrolyzed/milligram protein/min. (
conditions have not yet been optimized). The activity is more than 50Z 
inhibited by either 10 uM vanadate, 1 mM N-ethyl maleimide or by 5 mM 
AMP-PNP. The ATPase is enhanced 50Z by 0.2Z Triton X-100.   These 
properties are dynein-like. When the 20 S protein is mixed with either 
microtubules or flagellar axonemes on slide, it promotes 
a nucleotide triphosphate-dependent microtubule translocation. 
Axonemes glide with their 'plus' ends trailing. These properties are 
kinesin-like. However, microtubules move at about 0.8 - 1.0 um/sec., 
about twice as fast as with kinesin under conditions of saturating ATP.
Furthermore, the motion is ATP-specific and is blocked by either 10 
uM vanadate, 1mM N-ethyl maleimide, or by 0.5 mM ATP-gamma-S. Motility 
is slowed but not blocked by [AMP-PNP] = [ATP]. These characteristics 
and the presence of an ATPase activity differ from the properties 
described for kinesin. The roughly parallel inhibition of the ATPase 
and the motility by several reagents suggests that the enzyme activity 
and the motility are caused by the same protein or protein complex. We 
therefore propose that the 400 K protein from C. 
rotubule translocator which possesses 
properties of both dynein and kinesin.