title: Tubulin assembly in the presence of calcium ions and taxol: microtubule bundling and formation of macrotubule-ring complexes.
abstract: It has been confirmed that taxol is able to prevent Ca(2+)-induced inhibition of microtubule formation from tubulin in the presence of microtubule-associated proteins. However, by means of electron microscopy and scanning force microscopy it could be demonstrated that assembly in the presence of Ca2+ and taxol leads to structural aberrations. The kind of aberration depends on the order of addition of taxol and Ca2+ to tubulin. When taxol was added first, microtubules were formed preferentially. But, these microtubules typically associated with each other by close wall-to-wall alignments or they formed complexes with some C-shaped protofilament ribbons, resulting in microtubule bundles or doublet- and triplet-like microtubule structures, respectively. When Ca2+ was added first, macrotubules, rings, and ring crystals were the dominant assembly products. Mostly, the macrotubules were also bundled or they enclosed rings in their lumen. The findings clearly demonstrate the potency of Ca2+ to induce different polymorphic assemblies with additional protofilament associations, not realized in microtubules.
authors.affiliation: Institute of Molecular Biotechnology, Research Group of Electron Microscopy and Molecular Cytology, Jena, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Vater
authors.forename: K J
authors.initials: KJ
authors.lastname: Böhm
authors.forename: E
authors.initials: E
authors.lastname: Unger
mesh_terms: D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology*; D008868:Microtubule Proteins / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D008870:Microtubules / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure; D017239:Paclitaxel / Q000494:pharmacology*; D013552:Swine; D014404:Tubulin / Q000187:drug effects* / Q000502:physiology / Q000648:ultrastructure
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D008868:Microtubule Proteins; D014404:Tubulin; D017239:Paclitaxel; D002118:Calcium