title: Factors implicated in determining the structure of zinc tubulin-sheets: lateral tubulin-tubulin interaction is promoted by the presence of zinc.
abstract: Addition of increasing amounts of zinc to a cold microtubule protein solution results in the disappearance of 30 S oligomer found in the absence of that cation and in the appearance of new tubulin oligomers, 90 S and 23 S. When a microtubule protein solution is warmed in the presence of zinc, tubulin-sheets are assembled. We have tested the influence of microtubule associated proteins and the zinc:tubulin ratio on the polymerization process. Depletion of microtubule associated proteins results in wider and longer tubulin-sheets than those polymerized in the presence of microtubule associated proteins. However by increasing zinc concentration wider but shorter tubulin-sheets were found. These results suggest that microtubule associated proteins and zinc could promote nucleation of tubulin-sheets, but zinc also promotes lateral tubulin-tubulin interaction. This interpretation was confirmed when microtubule protein was assembled at a low zinc:tubulin ratio. In such conditions composite structures of microtubules and zinc tubulin-sheets are formed. These composite structures are consequence of a lateral attachment of a zinc tubulin-sheet on a microtubule protofilament.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D066298:In Vitro Techniques; D008870:Microtubules / Q000378:metabolism*; D009711:Nucleotides / Q000378:metabolism; D011487:Protein Conformation; D013552:Swine; D014404:Tubulin / Q000378:metabolism*; D015032:Zinc / Q000378:metabolism*
chemical_list: D009711:Nucleotides; D014404:Tubulin; D015032:Zinc