title: The prion curing agent guanidinium chloride specifically inhibits ATP hydrolysis by Hsp104.
abstract: The molecular chaperone Hsp104 from Saccharomyces cerevisiae dissolves protein aggregates in the cell and is thus of crucial importance for the thermotolerance of yeast. In addition to this disaggregase activity, Hsp104 has a key function in yeast prion propagation, as Hsp104 was found to be essential for the maintenance of the associated phenotypes. In vivo data suggest that Hsp104 function is affected by guanidinium chloride. Adding small amounts of this compound to yeast medium causes curing of the prions: cells lose their prion-related phenotype. Guanidinium chloride was also found to impair heat shock resistance. Here, we present a detailed in vitro analysis showing that guanidinium chloride is an uncompetitive inhibitor of Hsp104. Micromolar concentrations of this agent reduce the ATPase activity of Hsp104 to approximately 35% of its normal activity. This inhibition is not related to the denaturing properties of this compound, because Hsp104 was not affected by urea. Guanidinium ions selectively bind to the nucleotide-bound, hexameric state of the molecular chaperone. Thus, they increase the affinity of Hsp104 for adenine nucleotides and promote the nucleotide-dependent oligomerization of the chaperone. Our findings strongly suggest that guanidinium chloride causes curing of yeast prions by perturbing the ATPase of Hsp104, which is essential for both prion propagation and thermotolerance.
authors.affiliation: Institut für Organische Chemie und Biochemie, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany.
authors.forename: Valerie
authors.initials: V
authors.lastname: Grimminger
authors.forename: Klaus
authors.initials: K
authors.lastname: Richter
authors.forename: Axel
authors.initials: A
authors.lastname: Imhof
authors.forename: Johannes
authors.initials: J
authors.lastname: Buchner
authors.forename: Stefan
authors.initials: S
authors.lastname: Walter
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019791:Guanidine / Q000378:metabolism / Q000494:pharmacology*; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D046911:Macromolecular Substances; D011328:Prions / Q000737:chemistry / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000201:enzymology; D029701:Saccharomyces cerevisiae Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D006360:Heat-Shock Proteins; D046911:Macromolecular Substances; D011328:Prions; D029701:Saccharomyces cerevisiae Proteins; C070972:HsP104 protein, S cerevisiae; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D019791:Guanidine