MICROTUBULAR ORGANIZATION IN TOBACCO CELLS - HEAT-SHOCK-PROTEIN-90 CAN BIND TO TUBULIN IN-VITRO

The heat-shock protein 90 (HSP90) from tobacco VBI-O cells specificall y binds to nitrocellulose that had been coated with polymerized microt ubules or tubulin dimers. HSP90 is expressed preferentially during cel l division and becomes downregulated during cell elongation. HSP90 cof ractionates with tubulin dimers during affinity chromatography with se pharose coupled to the tubulin-binding drug ethyl N-phenylcarbamate (E PC). Binding of HSP90 to EPC-sepharose depends on the presence of tubu lin. Antibodies against tubulin and HSP90 immunoadsorb HSP90 and tubul in, respectively. These results demonstrate that HSP90 behaves as a mi crotubule-binding protein in vitro.