Spermine—a polyamine found in eukaryotic cells—mediates the assembly of taxol-stabilized microtubules into hexagonally packed bundles. It is now shown with electron microscopy and small-angle X-ray scattering that at higher concentrations of spermine the bundles disassemble and then reassemble into inverted tubulin tubules that expose the inner surface of the precursor microtubules, and that this results from spermine triggering a straight-to-curved conformation transition in the taxol-stabilized tubulin oligomers.
- Miguel A. Ojeda-Lopez
- Daniel J. Needleman
- Cyrus R. Safinya
