Probing the Pore Drug Binding Site of Microtubules with Fluorescent Taxanes: Evidence of Two Binding Poses

SummaryThe pore site in microtubules has been studied with the use of Hexaflutax, a fluorescent probe derived from paclitaxel. The compound is active in cells with similar effects to paclitaxel, indicating that the pore may be a target to microtubule stabilizing agents. While other taxanes bind microtubules in a monophasic way, thus indicating a single type of sites, Hexaflutax association is biphasic. Analysis of the phases indicates that two different binding sites are detected, reflecting two different modes of binding, which could arise from different arrangements of the taxane or fluorescein moieties in the pore. Association of the 4-4-20 antifluorescein monoclonal antibody-Hexaflutax complex to microtubules remains biphasic, thus indicating that the two phases observed arise from two different poses of the taxane moiety.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (427 K)Download as PowerPoint slideHighlights► The pore site of microtubules is a pharmacological target for antitumoral drugs ► The pore site is inhomogeneous with at least two different binding possibilities