HSP70 and HSP90 homologs are associated with tubulin in hetero-oligomeric complexes, cilia and the cortex of Tetrahymena

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Abstract
We show in the present study that homologs of hsp90 and hsp70 are induced by heat shocks in Tetrahymena and appear to form a high molecular mass complex (∼700 kDa) with tubulin. Three members of the hsp70 family (hsp72, 73, and 78) and one member of the hsp90 family (hsp82) have been identified by immunological or by a combination of immunological and sequencing methods. The known components of the 700 kDa complex and the conditions under which it can be recovered suggest that it may be an induced protective assemblage rather than a normal processing intermediate. Immunoblotting and immunofluorescence studies suggest further that large amounts of hsp73 and lesser amounts of hsp82 are associated with mature microtubules in both cilia and the cortex in this cell type. Some site-specific localizations of the identified heat shock proteins were also noted in non-microtubular components of the cell cortex.