Exposure of lumenal microtubule sites after mild fixation

High-resolution analysis of tubulin structure and docking the structure of tubulin dimer into a map of microtubules led to a prediction that sites for tubulin acetylation are in the interior of microtubules, This is somehow d ifficult to reconcile with their susceptibility to proteases and acetylatio n in assembled microtubules, To assess the availability of acetylated alpha -tubulin for antibodies, immunofluorescence on detergent-extracted cells, on cells fixed under various conditions and in micro-injected cells,Fas per formed with monoclonal antibodies of known epitope locations. The presented data indicate that acetylated alpha :Lys40 is not exposed on unfixed micro tubules but that this region of lumenal microtubule surface becomes easily exposed under mild fixation conditions.