Kinesin-driven microtubule motility in the presence of alkaline-earth metal ions: Indication for a calcium ion-dependent motility
✍ Scribed by Böhm, K.J. ;Steinmetzer, P. ;Daniel, A. ;Baum, M. ;Vater, W. ;Unger, E.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 183 KB
- Volume
- 37
- Category
- Article
- ISSN
- 0886-1544
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✦ Synopsis
We studied the effect of alkaline-earth metal ions on the kinesin-driven gliding of microtubules, using a narrow glass chamber enabling the exchange of buffer components without interrupting microscopic observation. Under standard conditions (0.5 mM Mg 21 ), microtubules were found to glide at a mean velocity of about 0.6 µm/s. Motility was widely ceased after removing Mg 21 . Subsequent addition of Ca 21 restored motility (maximal mean gliding velocity measured: 0.26 µm/s at 2.5 mM Ca 21 ). Also in the presence of Sr 21 or Ba 21 a slow gliding could be observed (0.025 µm/s and 0.014 µm/s, respectively, at 0.5 mM). After removal of Ca 21 , Sr 21 , or Ba 21 and re-addition of Mg 21 , the gliding velocities reached approximately the values determined under standard conditions. Motility was not changed when 0.5 mM Ca 21 , Sr 21 , or Ba 21 were applied together with Mg 21 .
Microtubule gliding stopped after substitution of 0.5 mM BeCl 2 for Mg 21 . When both BeCl 2 and Mg 21 were present, the mean gliding velocity was reduced to 0.29 µm/s. In addition, many microtubules were released from the kinesincoated glass surface, indicating that the beryllium salt disorders the binding between kinesin and microtubules.
Our results confirm that Mg 21 is the most suitable cofactor for kinesindriven microtubule motility. However, they also demonstrate that brain kinesin can generate motility when Ca 21 was substituted for Mg 21 . Cell Motil.