Prion-impairing mutations in Hsp70 chaperone Ssa1: effects on ATPase and chaperone activities
Graduate School of Biomedical Sciences; Laboratory of Biochemistry and Genetics
Medical Subject Headings
Adenosine Triphosphatases; Amino Acid Substitution; Binding Sites; Genes, Fungal; HSP70 Heat-Shock Proteins; Models, Molecular; Molecular Chaperones; Mutagenesis, Site-Directed; Prions; Protein Structure, Tertiary; Recombinant Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
Life Sciences | Medicine and Health Sciences
We previously described many Hsp70 Ssa1p mutants that impair [PSI(+)] prion propagation in yeast without affecting cell growth. To determine how the mutations alter Hsp70 we analyzed biochemically the substrate-binding domain (SBD) mutant L483W and the nucleotide-binding domain (NBD) mutants A17V and R34K. Ssa1(L483W) ATPase activity was elevated 10-fold and was least stimulated by substrates or Hsp40 co-chaperones. Ssa1(A17V) and Ssa1(R34K) ATPase activities were nearly wild type but both showed increased stimulation by substrates. Peptide binding and reactivation of denatured luciferase were enhanced in Ssa1(A17V) and Ssa1(R34K) but compromised in Ssa1(L483W). The nucleotide exchange factor Fes1 influenced ATPase of wild type Ssa1 and each mutant differently. Partial protease digestion uncovered similar and distinct conformational changes of the substrate-binding domain among the three mutants. Our data suggest that prion-impairing mutations of Ssa1 can increase or decrease substrate interactions, alter the Hsp70 reaction cycle at different points and impair normal NBD-SBD cooperation.
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Citation: Arch Biochem Biophys. 2008 Oct 15;478(2):167-74. Epub 2008 Aug 6. Link to article on publisher's site
Archives of biochemistry and biophysics
Needham, Patrick G. and Masison, Daniel C., "Prion-impairing mutations in Hsp70 chaperone Ssa1: effects on ATPase and chaperone activities" (2008). GSBS Student Publications. 1581.