2ygf
From Proteopedia
L89V, L93I and V136M Mutant of N-Term HSP90 complexed with Geldanamycin
Structural highlights
FunctionHSP82_YEAST Molecular chaperone that promotes the maturation, structural maintenance and proper regulation of specific target proteins involved in cell cycle control and signal transduction. Undergoes a functional cycle that is linked to its ATPase activity. The nucleotide-free form of the dimer is found in an open conformation in which the N-termini are not dimerized and the complex is ready for client protein binding. Binding of ATP induces large conformational changes, resulting in the formation of a ring-like closed structure in which the N-terminal domains associate intramolecularly with the middle domain and also dimerize with each other, stimulating their intrinsic ATPase activity and acting as a clamp on the substrate. Finally, ATP hydrolysis results in the release of the substrate. This cycle probably induces conformational changes in the client proteins, thereby causing their activation. Interacts dynamically with various co-chaperones that modulate its substrate recognition, ATPase cycle and chaperone function. Required for growth at high temperatures.[1] Publication Abstract from PubMedMuch attention is focused on the benzoquinone ansamycins as anticancer agents, with several derivatives of the natural product geldanamycin (GdA) now in clinical trials. These drugs are selective inhibitors of Hsp90, a molecular chaperone vital for many of the activities that drive cancer progression. Mutational changes to their interaction site, the extremely conserved ATP binding site of Hsp90, would mostly be predicted to inactivate the chaperone. As a result, drug resistance should not arise readily this way. Nevertheless, Streptomyces hygroscopicus, the actinomycete that produces GdA, has evolved an Hsp90 family protein (HtpG) that lacks GdA binding. It is altered in certain of the highly conserved amino acids making contacts to this antibiotic in crystal structures of GdA bound to eukaryotic forms of Hsp90. Two of these amino acid changes, located on one side of the nucleotide-binding cleft, weakened GdA/Hsp90 binding and conferred partial GdA resistance when inserted into the endogenous Hsp90 of yeast cells. Crystal structures revealed their main effect to be a weakening of interactions with the C-12 methoxy group of the GdA ansamycin ring. This is the first study to demonstrate that partial GdA resistance is possible by mutation within the ATP binding pocket of Hsp90.-Millson, S. H., Chua, C.-S., Roe, S. M., Polier, S., Solovieva, S., Pearl, L. H., Sim, T.-S., Prodromou, C., Piper, P. W. Features of the Streptomyces hygroscopicus HtpG reveal how partial geldanamycin resistance can arise with mutation to the ATP binding pocket of a eukaryotic Hsp90. Features of the Streptomyces hygroscopicus HtpG reveal how partial geldanamycin resistance can arise with mutation to the ATP binding pocket of a eukaryotic Hsp90.,Millson SH, Chua CS, Roe SM, Polier S, Solovieva S, Pearl LH, Sim TS, Prodromou C, Piper PW FASEB J. 2011 Nov;25(11):3828-37. Epub 2011 Jul 21. PMID:21778327[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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