Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.1.3 (ATPase)
 65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The translation of a heat shock protein (HSP), TGroEL, of thermophilic bacterium PS3 increased within 10 minutes when the culture temperature was raised from 60 degrees C to 70 degrees C. In contrast to hyperthermophilic HSPs such as Pyrodictium ATPase, TGroEL is homologous to GroEL of E. coli (Tamada et al. (1991) Biochem. Biophys. Res. Commun. 197, 565-571). The promoter of the thermophilic heat shock gene (tgrE) was sequenced to analyze the heat shock response. The sequences of the promoter were CCTACTTGCA (-35 region) and GTTCATTAATA (-10 region), which are more heat labile than those of the sigma 32 recognition sites of GroEL. The expression of this homologous tgrE in E. coli may be lethal to the cells. The ATPase alpha subunit of this thermophile is also homologous to TGroEL.
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PMID:Heat shock promoter of thermophilic chaperonin operon. 809 82

Deoxyspergualin (DSG), a spermidinyl, alpha-hydroxyglycyl, 7-guanidinoheptanoyl peptidomimetic, shows immunosuppressive activity. In confirmation of a recent report that immobilized methoxyDSG selectively retains the heat shock protein Hsc70, we report here quantitative binding of DSG and analogs to both Hsc70 and the 90-kDa heat shock protein Hsp90. We have utilized affinity capillary electrophoresis to obtain Kd values for DSG and analogs, and stimulation of the ATPase activity of Hsc70 to obtain Km values for DSG, that are comparable and corroborative. Kd values are 4 microM for DSG binding to Hsc70 and 5 microM for DSG binding to Hsp90. Two active analogs, methoxy- and glycylDSG, bind with similar affinities. Glyoxylylspermidine and des(aminopropyl)DSG, two inactive metabolites, have much reduced affinity for Hsc70 and Hsp90. These data validate binding of these novel immunosuppressant agents to these molecular chaperones, at concentrations in the range of pharmacologically active doses, and indicate that further characterization of Hsc70 and/or Hsp90 as potential targets for DSG is warranted.
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PMID:Quantitation of the interaction of the immunosuppressant deoxyspergualin and analogs with Hsc70 and Hsp90. 811 17

The bovine brain uncoating ATPase, a constitutive 70-kDa heat shock protein, uncoats clathrin-coated vesicles in an ATP-dependent reaction. The uncoating ATPase-clathrin complex formed from the uncoating reaction was compared to the complex formed by directly binding free clathrin to uncoating ATPase. The amount of the latter complex shows a simple hyperbolic dependence on either free clathrin or free uncoating ATPase concentration, whichever is in excess, with a binding stoichiometry of one uncoating ATPase per clathrin heavy chain. ATP markedly increases the rates of formation and dissociation of this complex while ADP profoundly inhibits these rates. At low uncoating ATPase concentrations, much more complex is formed by uncoating than by directly binding clathrin to enzyme. However, during column chromatography or dilution for electron microscopy, both types of complex dissociate in ATP but not ADP, and electron microscopy of both types of complex diluted into ADP shows binding only to the vertex of the clathrin triskelion. We conclude that the uncoating ATPase forms only one type of complex with clathrin and has only one site for nucleotide; ADP at this site prevents either formation or dissociation of complex, whereas ATP at this site allows both processes to occur rapidly.
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PMID:Complex formation between clathrin and uncoating ATPase. 812 55

It has recently been reported that the ATPase activity of DnaK, a 70 kDa heat shock protein from E. coli, is autostimulated by increasing protein concentration [(1993) FEBS Lett. 322, 277-279], suggesting that the DnaK dimer may be the enzymatically active species. In this paper we investigated the ATPase activity of different DnaK preparations; we found that the turnover number was very dependent on protein purification. With HPLC-purified DnaK we found a turnover number 20- to 50-fold lower than typical values previously published and no evidence of autostimulation, indicating that the monomer is the active species.
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PMID:DnaK ATPase activity revisited. 826 93

The heat shock protein ClpB in Escherichia coli is a protein-activated ATPase and consists of two proteins with sizes of 93 and 79 kDa. By polymerase chain reaction-aided site-directed mutagenesis, both the proteins have been shown to be encoded by the same reading frame of the clpB gene, the 93-kDa protein (ClpB93) from the 5'-end AUG translational initiation site and the 79-kDa protein (ClpB79) from the 149th codon (an internal GUG start site). Both the purified ClpB93 and ClpB79 proteins behave as tetrameric complexes with a very similar size of about 350 kDa upon gel filtration on a Superose-6 column. Both appear to be exclusively localized to the cytosol of E. coli. Both show inherent ATPase activities and have an identical Km of 1.1 mM for ATP. The ATPase activity of ClpB93 is as markedly stimulated by proteins, including casein and insulin, as that of wild-type ClpB, but the same proteins show little or no effect on ClpB79. Because ClpB79 lacks the 148 N-terminal sequence of ClpB93 but retains the two consensus sequences for adenine nucleotide binding, the N-terminal portion appears to contain a site(s) or domain(s) responsible for protein binding. Furthermore, ClpB79 is capable of inhibiting the casein-activated ATPase activity of ClpB93 in a dose-dependent manner but without any effect on its inherent ATPase activity. In addition, ClpB93 mixed with differing amounts of ClpB79 behave as tetrameric molecules, although its protein-activated ATPase activity is gradually reduced. These results suggest that tetramer formation between ClpB93 and ClpB79 may be responsible for the inhibition of the activity.
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PMID:Site-directed mutagenesis of the dual translational initiation sites of the clpB gene of Escherichia coli and characterization of its gene products. 837 77

We have continued our studies on the import pathway of the precursor to yeast cytochrome c oxidase subunit Va (pVa), a mitochondrial inner membrane protein. Previous work on this precursor demonstrated that import of pVa is unusually efficient, and that inner membrane localization is directed by a membrane-spanning domain in the COOH-terminal third of the protein. Here we report the results of studies aimed at analyzing the intramitochondrial sorting of pVa, as well as the role played by ancillary factors in import and localization of the precursor. We found that pVa was efficiently imported and correctly sorted in mitochondria prepared from yeast strains defective in the function of either mitochondrial heat shock protein (hsp)60 or hsp70. Under identical conditions the import and sorting of another mitochondrial protein, the precursor to the beta subunit of the F1 ATPase, was completely defective. Consistent with previous results demonstrating that the subunit Va precursor is loosely folded, we found that pVa could be efficiently imported into mitochondria after translation in wheat germ extracts. This results suggests that normal levels of extramitochondrial hsp70 are also not required for import of the protein. The results of this study enhance our understanding of the mechanism by which pVa is routed to the mitochondrial inner membrane. They suggest that while the NH2 terminus of pVa is exposed to the matrix and processed by the matrix metalloprotease, the protein remains anchored to the inner membrane before being assembled into a functional holoenzyme complex.
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PMID:Intramitochondrial sorting of the precursor to yeast cytochrome c oxidase subunit Va. 838 75

The heat shock response is an inducible protective system of all living cells. It simultaneously induces both heat shock proteins and an increased capacity for the cell to withstand potentially lethal temperatures (an increased thermotolerance). This has lead to the suspicion that these two phenomena must be inexorably linked. However, analysis of heat shock protein function in Saccharomyces cerevisiae by molecular genetic techniques has revealed only a minority of the heat shock proteins of this organism having appreciable influences on thermotolerance. Instead, physiological perturbations and the accumulation of trehalose with heat stress may be more important in the development of thermotolerance during a preconditioning heat shock. Vegetative S. cerevisiae also acquires thermotolerance through osmotic dehydration, through treatment with certain chemical agents and when, due to nutrient limitation, it arrests growth in the G1 phase of the cell cycle. There is evidence for the activities of the cAMP-dependent protein kinase and plasma membrane ATPase being very important in thermotolerance determination. Also, intracellular water activity and trehalose probably exert a strong influence over thermotolerance through their effects on stabilisation of membranes and intracellular assemblies. Future investigations should address the unresolved issue of whether the different routes to thermotolerance induction cause a common change to the physical state of the intracellular environment, a change that may result in an increased stabilisation of cellular structures through more stable hydrogen bonding and hydrophobic interactions.
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PMID:Molecular events associated with acquisition of heat tolerance by the yeast Saccharomyces cerevisiae. 839 11

The role of mitochondrial 70-kD heat shock protein (mt-hsp70) in protein translocation across both the outer and inner mitochondrial membranes was studied using two temperature-sensitive yeast mutants. The degree of polypeptide translocation into the matrix of mutant mitochondria was analyzed using a matrix-targeted preprotein that was cleaved twice by the processing peptidase. A short amino-terminal segment of the preprotein (40-60 amino acids) was driven into the matrix by the membrane potential, independent of hsp70 function, allowing a single cleavage of the presequence. Artificial unfolding of the preprotein allowed complete translocation into the matrix in the case where mutant mt-hsp70 had detectable binding activity. However, in the mutant mitochondria in which binding to mt-hsp70 could not be detected the mature part of the preprotein was only translocated to the intermembrane space. We propose that mt-hsp70 fulfills a dual role in membrane translocation of preproteins. (a) Mt-hsp70 facilitates unfolding of the polypeptide chain for translocation across the mitochondrial membranes. (b) Binding of mt-hsp70 to the polypeptide chain is essential for driving the completion of transport of a matrix-targeted preprotein across the inner membrane. This second role is independent of the folding state of the preprotein, thus identifying mt-hsp70 as a genuine component of the inner membrane translocation machinery. Furthermore we determined the sites of the mutations and show that both a functional ATPase domain and ATP are needed for mt-hsp70 to bind to the polypeptide chain and drive its translocation into the matrix.
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PMID:A dual role for mitochondrial heat shock protein 70 in membrane translocation of preproteins. 840 91

The Saccharomyces cerevisiae nuclear gene for a 78-kDa mitochondrial heat shock protein (hsp78) was identified in a lambda gt11 expression library through immunological screening with an hsp78-specific monoclonal antibody. Sequencing of HSP78 revealed a long open reading frame capable of encoding an 811-amino-acid, 91.3-kDa basic protein with a putative mitochondrial leader sequence and two potential nucleotide-binding sites. Sequence comparisons revealed that hsp78 is a member of the highly conserved family of Clp proteins and is most closely related to the Escherichia coli ClpB protein, which is thought to be an ATPase subunit of an intracellular ATP-dependent protease. The steady-state levels of HSP78 transcripts and protein varied in response to both thermal stress and carbon source with an approximately 30-fold difference between repressed levels in cells growing fermentatively on glucose at 30 degrees C and derepressed levels in heat-shocked cells growing on a nonfermentable carbon source. The response to heat shock is consistent with the presence of a characteristic heat shock regulatory element in the 5'-flanking DNA. Submitochondrial fractionation showed that hsp78 is a soluble protein located in the mitochondrial matrix. Cells carrying disrupted copies of HSP78 lacked hsp78 but were not impaired in respiratory growth at normal and elevated temperatures or in the ability to survive and retain mitochondrial function after thermal stress. The absence of a strong mitochondrial phenotype in hsp78 mutants is comparable to the nonlethal phenotypes of mutations in other Clp genes in bacteria and yeast. HSP78 is the third gene, with SSC1 and HSP60, known to encode a yeast mitochondrial heat shock protein and the second gene, with HSP104, for a yeast ClpB homolog.
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PMID:HSP78 encodes a yeast mitochondrial heat shock protein in the Clp family of ATP-dependent proteases. 841 29

Immunoglobulin-binding protein (BiP), a 70-kDa heat shock protein in the endoplasmic reticulum, binds transiently to nascent proteins, releasing them upon folding and assembly. The in vitro release of bound proteins from BiP requires ATP hydrolysis. Recently, the three-dimensional structure was solved for an ATP-hydrolyzing proteolytic 44-kDa fragment of a 71-kDa heat shock cognate protein, HSC71. Because of the high degree of homology in this region, BiP presumably forms a similar ATP binding structure. Amino-terminal deletions in BiP eliminated ATP-agarose binding. Alteration of a second potential ATP binding site had no effect, suggesting that only the HSC71-like site was capable of ATP binding. Crystallographic data from HSC71 implicated certain amino acids in interactions with the beta-phosphate, gamma-phosphate, and divalent cation of ATP. Mutation of each corresponding residue in BiP (Thr-37, Thr-229, and Glu-201) severely inhibited its ATPase activity. These BiP mutants were still capable of binding ATP and immunoglobulin heavy chains, suggesting that these mutations did not drastically alter the structure of BiP. They did however block the ATP-mediated release of heavy chains from BiP. Our results demonstrate that the structure of BiP in this region must be extremely similar to that elucidated for HSC71 and that mutations of residues proposed to interact with ATP block the ATP-mediated release of bound protein by inhibiting ATP hydrolysis.
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PMID:Mutations within the nucleotide binding site of immunoglobulin-binding protein inhibit ATPase activity and interfere with release of immunoglobulin heavy chain. 846 60


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