Binding of Immunophilins to the 90 kDa Heat Shock Protein (hsp90) via a Tetratricopeptide Repeat Domain Is a Conserved Protein Interaction in Plants
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- 作者：Janet K. Owens-Grillo ; Louis F. Stancato ; Kai Hoffmann ; William B. Pratt ; and Priti Krishna
- 刊名：Biochemistry
- 出版年：1996
- 出版时间：December 3, 1996
- 年：1996
- 卷：35
- 期：48
- 页码：15249 - 15255
- 全文大小：362K
- 年卷期：v.35,no.48(December 3, 1996)
- ISSN：1520-4995
文摘
In animal cell lysates, multiprotein complexes containing hsp90,hsp70, p60, p23, and severalimmunophilins can assemble steroid receptors and oncogenic proteinkinases, such as v-Src and v-Raf,into heterocomplexes that contain hsp90 and either immunophilins or, inthe case of protein kinases, p50.The complexes with hsp90 are required for the proper functioningof these signal transduction systems.Wheat germ lysate contains a similar protein folding activity thatforms functional steroid receptorcomplexes with hsp90, but not all the components of this system havebeen identified. The plant chaperonesystem has conserved interactions with animal chaperones in that wheathsp70 functions in the rabbitreticulocyte lysate heterocomplex assembly system and human p23functions in the wheat germ lysate.Here, we ask if wheat germ lysate also contains immunophilins ofthe FK506-binding class (FKBPs) thatbind to the hsp90 component of the chaperone complex viatetratricopeptide repeat (TPR) domains. Todemonstrate the plant heterocomplex, we add purified mammalian p23,preadsorbed with the JJ3 antibodyto protein A-Sepharose, to wheat germ lysate and allow ATP-dependentformation of an animal p23·plant hsp90 complex. The complex is then washed and incubatedwith the radiolabeled immunosuppressantdrug [3H]FK506, which binds in a specific manner toa coimmunoadsorbed plant FKBP. Binding of theplant FKBP to plant hsp90 is prevented by adding to wheat germ lysate apurified fragment containingthe TPR domains of human cyclophilin-40. Geldanamycin, abenzoquinone ansamycin that binds to animalhsp90s and prevents their chaperone activity, binds in atemperature-dependent manner to wheat hsp90 toblock formation of the p23·hsp90·FKBP heterocomplex.These data show that immunophilin binding tohsp90 via TPR domains is conserved in the plant kingdom aswell as in the animal kingdom and thatgeldanamycin will be an important tool for the study of hsp90-mediatedprotein chaperoning in plantcells.