title: Interaction of radicicol with members of the heat shock protein 90 family of molecular chaperones.
abstract: The Hsp90 family of proteins in mammalian cells consists of Hsp90 alpha and beta, Grp94, and Trap-1 (Hsp75). Radicicol, an antifungal antibiotic that inhibits various signal transduction proteins such as v-src, ras, Raf-1, and mos, was found to bind to Hsp90, thus making it the prototype of a second class of Hsp90 inhibitors, distinct from the chemically unrelated benzoquinone ansamycins. We have used two novel methods to immobilize radicicol, allowing for detailed analyses of drug-protein interactions. Using these two approaches, we have studied binding of the drug to N-terminal Hsp90 point mutants expressed by in vitro translation. The results point to important drug contacts with amino acids inside the N-terminal ATP/ADP-binding pocket region and show subtle differences when compared with geldanamycin binding. Radicicol binds more strongly to Hsp90 than to Grp94, the Hsp90 homolog that resides in the endoplasmic reticulum. In contrast to Hsp90, binding of radicicol to Grp94 requires both the N-terminal ATP/ADP-binding domain as well as the adjacent negatively charged region. Radicicol also specifically binds to yeast Hsp90, Escherichia coli HtpG, and a newly described tumor necrosis factor receptor-interacting protein, Trap-1, with greater homology to bacterial HtpG than to Hsp90. Thus, the radicicol-binding site appears to be specific to and is conserved in all members of the Hsp90 family of molecular chaperones from bacteria to mammals, but is not present in other molecular chaperones with nucleotide-binding domains.
authors.affiliation: Medicine Branch, National Cancer Institute, National Institutes of Health, Rockville, Maryland 20850, USA.
authors.forename: T W
authors.initials: TW
authors.lastname: Schulte
authors.forename: S
authors.initials: S
authors.lastname: Akinaga
authors.forename: T
authors.initials: T
authors.lastname: Murakata
authors.forename: T
authors.initials: T
authors.lastname: Agatsuma
authors.forename: S
authors.initials: S
authors.lastname: Sugimoto
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
authors.forename: B B
authors.initials: BB
authors.lastname: Simen
authors.forename: Y
authors.initials: Y
authors.lastname: Argon
authors.forename: S
authors.initials: S
authors.lastname: Felts
authors.forename: D O
authors.initials: DO
authors.lastname: Toft
authors.forename: L M
authors.initials: LM
authors.lastname: Neckers
authors.forename: S V
authors.initials: SV
authors.lastname: Sharma
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D016227:Benzoquinones; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D019921:Biotinylation; D002461:Cell Line, Transformed; D002846:Chromatography, Affinity; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D047029:Lactams, Macrocyclic; D007783:Lactones / Q000737:chemistry / Q000378:metabolism*; D018942:Macrolides; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D018832:Molecular Chaperones / Q000378:metabolism*; D009154:Mutation; D011485:Protein Binding; D011809:Quinones / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D001426:Bacterial Proteins; D016227:Benzoquinones; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D007783:Lactones; D018942:Macrolides; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011809:Quinones; C018551:glucose-regulated proteins; C035359:monorden; C001277:geldanamycin