Kinesin-driven microtubule motility in the presence of alkaline-earth metal ions: indication for a calcium ion-dependent motility.
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 Mg2+), microtubules were found to glide at a mean velocity of about 0.6 micron/s. Motility was widely ceased after removing Mg2+. Subsequent addition of Ca2+ restored motility (maximal mean gliding velocity measured: 0.26 micron/s at 2.5 mM Ca2+). Also in the presence of Sr2+ or Ba2+ a slow gliding could be observed (0.025 micron/s and 0.014 micron/s, respectively, at 0.5 mM). After removal of Ca2+, Sr2+, or Ba2+ and re-addition of Mg2+, the gliding velocities reached approximately the values determined under standard conditions. Motility was not changed when 0.5 mM Ca2+, Sr2+, or Ba2+ were applied together with Mg2+. Microtubule gliding stopped after substitution of 0.5 mM BeCl2 for Mg2+. When both BeCl2 and Mg2+ were present, the mean gliding velocity was reduced to 0.29 micron/s. In addition, many microtubules were released from the kinesin coated glass surface, indicating that the beryllium salt disorders the binding between kinesin and microtubules. Our results confirm that Mg2+ is the most suitable cofactor for kinesin driven microtubule motility. However, they also demonstrate that brain kinesin can generate motility when Ca2+ was substituted for Mg2+.
Böhm
K J
KJ
Institute of Molecular Biotechnology, Research Group of Electron Microscopy and Molecular Cytology, Jena, Germany.
Steinmetzer
P
P
Daniel
A
A
Baum
M
M
Vater
W
W
Unger
E
E
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D016547:Kinesins / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D008673:Metals, Alkaline Earth / Q000494:pharmacology*; D008870:Microtubules / Q000187:drug effects*; D009068:Movement / Q000187:drug effects*; D013552:Swine
D008673:Metals, Alkaline Earth; D016547:Kinesins; D008274:Magnesium; D002118:Calcium