Microtubular Organization in Tobacco Cells: Heat-Shock Protein 90 can Bind to Tubulin in Vitro

The heat-shock protein 90 (HSP90) from tobacco VBIo cells specifically binds to nitrocellulose that had been coated with polymerized microtubules or tubulin dimers. HSP90 is expressed preferentially during cell division and becomes downregulated during cell elongation. HSP90 cofractionates with tubulin dimers during affinity chromatography with sepharose coupled to the tubulin-binding drug ethyl N-phenylcarbamate (EPC). Binding of HSP90 to EPC-sepharose depends on the presence of tubulin. Antibodies against tubulin and HSP90 irnmunoadsorb HSP90 and tubulin, respectively, These results demonstrate that HSP90 behaves as a microtubule-binding protein in vitro.