Genetic evidence for a functional relationship between Hsp104 and Hsp70

Sánchez, Yolanda; Parsell, Dawn A.; Taulien, J; Vogel, Joseph P.; Craig, Elizabeth A.; Lindquist, Susan

doi:10.1128/jb.175.20.6484-6491.1993

Cited by 113 publications

(95 citation statements)

References 35 publications

(26 reference statements)

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“…Unlike many other chaperones, WT Hsp104 is not toxic to growth even when it is overexpressed at very high concentrations (28,29). The fact that K620T slightly inhibits growth at normal temperatures, but only in the presence of WT protein, suggests correct subunit interactions are normally required to control the biological activities of Hsp104.…”

Section: Discussionmentioning

confidence: 99%

“…Cells coexpressing K218T and WT Hsp104 at similar levels had normal levels of thermotolerance (D. A. Parsell and S.L., unpublished observations). However, very little functional Hsp104 is required for thermotolerance (28,29). Thus, those Hsp104 hexamers that do not contain sufficient K218T:A315T to block cooperative ATP hydrolysis by WT Hsp104 could well be sufficient for thermotolerance.…”

Section: Atp Hydrolysis Is Cooperative In Hexameric Hsp104mentioning

confidence: 99%

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Subunit interactions influence the biochemical and biological properties of Hsp104

Schirmer¹

2001

Proceedings of the National Academy of Sciences

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Point mutations in either of the two nucleotide-binding domains (NBD) of Hsp104 (NBD1 and NBD2) eliminate its thermotolerance function in vivo. In vitro, NBD1 mutations virtually eliminate ATP hydrolysis with little effect on hexamerization; analogous NBD2 mutations reduce ATPase activity and severely impair hexamerization. We report that high protein concentrations overcome the assembly defects of NBD2 mutants and increase ATP hydrolysis severalfold, changing Vmax with little effect on Km. In a complementary fashion, the detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate inhibits hexamerization of wildtype (WT) Hsp104, lowering Vmax with little effect on Km. ATP hydrolysis exhibits a Hill coefficient between 1.5 and 2, indicating that it is influenced by cooperative subunit interactions. To further analyze the effects of subunit interactions on Hsp104, we assessed the effects of mutant Hsp104 proteins on WT Hsp104 activities. An NBD1 mutant that hexamerizes but does not hydrolyze ATP reduces the ATPase activity of WT Hsp104 in vitro. In vivo, this mutant is not toxic but specifically inhibits the thermotolerance function of WT Hsp104. Thus, interactions between subunits influence the ATPase activity of Hsp104, play a vital role in its biological functions, and provide a mechanism for conditionally inactivating Hsp104 function in vivo.T he HSP100͞Clp family of chaperone proteins plays a wide variety of important cellular roles in different organisms, including survival of environmental stress, regulation of genetic competence, transposition, proteolysis, and control of a proteinbased genetic element (prion). These seemingly unrelated roles are unified by a common remarkable biochemical mechanism; the proteins promote the disassembly of aggregated proteins and higher-order protein complexes (reviewed in refs. 1 and 2). Several biochemical properties are shared by HSP100 proteins and are required for their biological functions, suggesting that these properties are important to the complex phenomenon of protein disassembly. These properties include an ATPhydrolyzing activity (3-10) and the ability to self-assemble into oligomers, primarily hexamers (11-13).A member of the HSP100 family from Saccharomyces cerevisiae, Hsp104, is critical for survival after exposure to extreme temperatures (50°C) (14) or high concentrations of ethanol (20%) (15). These stresses cause protein denaturation, and Hsp104 promotes survival by facilitating the resolubilization of heat-damaged, aggregated proteins (reviewed in refs. 1 and 2). At normal temperatures, Hsp104 plays a critical role in the inheritance of the novel proteinaceous genetic element [PSIϩ] (often called a yeast prion), an ordered aggregate of the translation terminator, Sup35 (16).Hsp104 is a member of the class 1 HSP100 proteins, with two distinct but highly conserved nucleotide-binding domains (NBDs) (1, 17). NBD1 and NBD2 of Hsp104 show only 22% amino acid identity with each other, yet each shares 40-60% identity with the corresponding domains of t...

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Section: Discussionmentioning

confidence: 99%

Section: Atp Hydrolysis Is Cooperative In Hexameric Hsp104mentioning

confidence: 99%

Subunit interactions influence the biochemical and biological properties of Hsp104

Schirmer¹

2001

Proceedings of the National Academy of Sciences

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“…Single proteins have been shown to confer tolerance to a stressful environment. Synthesis of Hsp104p appears to be required to acquire the state of thermotolerance (37), and in a genetic background without HSP104 expression, the SSA1 gene is linked to heat stress resistance (38). Synthesis of Ctt1p seems to partly but not fully account for the increased resistance to high NaCl concentrations acquired by short-time conditioning at low-level salinities (39).…”

Section: Discussionmentioning

confidence: 99%

Global changes in protein synthesis during adaptation of the yeast Saccharomyces cerevisiae to 0.7 M NaCl

Blomberg

1995

J Bacteriol

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Exponentially growing Saccharomyces cerevisiae was challenged to increased salinity by transfer to 0.7 M NaCl medium, and changes in protein synthesis were examined during the 1st h of adaptation by use of two-dimensional gel electrophoresis coupled to computerized quantification. An impressive number of proteins displayed changes in the relative rate of synthesis, with most differences from nonstressed cells being found at between 20 and 40 min. During this period, 18 proteins exhibited more than eightfold increases in their rates of synthesis and were classified as highly NaCl responsive. Only two proteins were repressed to the same level. Most of these highly NaCl-responsive proteins seemed to constitute gene products not earlier reported to respond to dehydration. Applying a selection criterion to subsequent samples of a twofold change in the relative rate of synthesis, 14 different regulatory patterns were discerned. Most identified glycolytic enzymes exhibited a delayed response, and their rates of synthesis did not change until the middle phase of adaptation, with only a minor decrease in the rate of production. A slight salt-stimulated response was observed for some members of the HSP70 gene family. Overall, the data presented indicate complex intracellular signalling as well as involvement of diverse regulatory mechanisms during the period of adaptation to NaCl.

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“…Protecting the cells against the damaging effects of various stresses is another function attributed to hsp70s (Welch and Feramisco, 1984;Sanchez et al, 1993), as well as other hsps (Landry et al, 1989;Sanchez and Lindquist, 1990;Sanchez et al, 1992) although the mechanism by which protection is generated is not well understood. Most stress conditions compromise the structural integrity of proteins, exposing otherwise hidden interactive domains.…”

Section: Stress and The Regulation Of The Heat-shock Responsementioning

confidence: 99%

Heat‐shock proteins as molecular chaperones

Becker

Craig

1994

European Journal of Biochemistry

479

221

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Functional proteins within cells are normally present in their native, completely folded form. However, vital processes of protein biogenesis such as protein synthesis and translocation of proteins into intracellular compartments require the protein to exist temporarily in an unfolded or partially folded conformation. As a consequence, regions buried when a polypeptide is in its native conformation become exposed and interact with other proteins causing protein aggregation which is deleterious to the cell. To prevent aggregation as proteins become unfolded, heat‐shock proteins protect these interactive surfaces by binding to them and facilitating the folding of unfolded or nascent polypeptides. In other instances the binding of heat‐shock proteins to interactive surfaces of completely folded proteins is a crucial part of their regulation. As heat shock and other stress conditions cause cellular proteins to become partially unfolded, the ability of heat‐shock proteins to protect cells against the adverse effects of stress becomes a logical extension of their normal function as molecular chaperones.

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Genetic evidence for a functional relationship between Hsp104 and Hsp70

Cited by 113 publications

References 35 publications

Subunit interactions influence the biochemical and biological properties of Hsp104

Subunit interactions influence the biochemical and biological properties of Hsp104

Global changes in protein synthesis during adaptation of the yeast Saccharomyces cerevisiae to 0.7 M NaCl

Heat‐shock proteins as molecular chaperones

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