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Chaperone Activity (chaperone + activity)
Selected AbstractsChaperone Activity of Bicyclic Nojirimycin Analogues for Gaucher Mutations in Comparison with N -(n -nonyl)DeoxynojirimycinCHEMBIOCHEM, Issue 17 2009Zhuo Luan Abstract Gaucher disease (GD), the most prevalent lysosomal storage disorder, is caused by mutations of lysosomal ,-glucosidase (acid ,-Glu, ,-glucocerebrosidase); these mutations result in protein misfolding. Some inhibitors of this enzyme, such as the iminosugar glucomimetic N -(n -nonyl)-1-deoxynojirimycin (NN-DNJ), are known to bind to the active site and stabilize the proper folding for the catalytic form, acting as "chemical chaperones" that facilitate transport and maturation of acid ,-Glu. Recently, bicyclic nojirimycin (NJ) analogues with structure of sp2 iminosugars were found to behave as very selective, competitive inhibitors of the lysosomal ,-Glu. We have now evaluated the glycosidase inhibitory profile of a series of six compounds within this family, namely 5- N,6- O -(N, -octyliminomethylidene-NJ (NOI-NJ), the 6-thio and 6-amino-6-deoxy derivatives (6S-NOI-NJ and 6N-NOI-NJ) and the corresponding galactonojirimycin (GNJ) counterparts (NOI-GNJ, 6S-NOI-GNJ and 6N-NOI-GNJ), against commercial as well as lysosomal glycosidases. The chaperone effects of four selected candidates (NOI-NJ, 6S-NOI-NJ, 6N-NOI-NJ, and 6S-NOI-GNJ) were further evaluated in GD fibroblasts with various acid ,-Glu mutations. The compounds showed enzyme enhancement on human fibroblasts with N188S, G202R, F213I or N370S mutations. The chaperone effects of the sp2 iminosugar were generally stronger than those observed for NN-DNJ; this suggests that these compounds are promising candidates for clinical treatment of GD patients with a broad range of ,-Glu mutations, especially for neuronopathic forms of Gaucher disease. [source] Chaperone activity of recombinant maize chloroplast protein synthesis elongation factor, EF-TuFEBS JOURNAL, Issue 18 2004Damodara Rao The protein synthesis elongation factor, EF-Tu, is a protein that carries aminoacyl-tRNA to the A-site of the ribosome during the elongation phase of protein synthesis. In maize (Zea mays L) this protein has been implicated in heat tolerance, and it has been hypothesized that EF-Tu confers heat tolerance by acting as a molecular chaperone and protecting heat-labile proteins from thermal aggregation and inactivation. In this study we investigated the effect of the recombinant precursor of maize EF-Tu (pre-EF-Tu) on thermal aggregation and inactivation of the heat-labile proteins, citrate synthase and malate dehydrogenase. The recombinant pre-EF-Tu was purified from Escherichia coli expressing this protein, and mass spectrometry confirmed that the isolated protein was indeed maize EF-Tu. The purified protein was capable of binding GDP (indicative of protein activity) and was stable at 45 °C, the highest temperature used in this study to test this protein for possible chaperone activity. Importantly, the recombinant maize pre-EF-Tu displayed chaperone activity. It protected citrate synthase and malate dehydrogenase from thermal aggregation and inactivation. To our knowledge, this is the first observation of chaperone activity by a plant/eukaryotic pre-EF-Tu protein. The results of this study support the hypothesis that maize EF-Tu plays a role in heat tolerance by acting as a molecular chaperone and protecting chloroplast proteins from thermal aggregation and inactivation. [source] Effects of salinity levels on proteome of Suaeda aegyptiaca leavesPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 8 2006Hossein Askari Abstract Saline soils are the major problem of cultivated lands of Iran. Suaeda aegyptiaca is a salt-tolerant plant (halophytes) that grow naturally in salt-affected areas of Iran. We have employed proteomics to identify the mechanisms of salt responsiveness in leaves of S.,aegyptiaca grown under different salt concentrations. Ten-day-old plants were treated with 0, 150, 300, 450, and 600,mM NaCl. After 30,days of treatment, leaf samples were collected and analyzed using 2-D-PAGE. Out of 700,protein spots reproducible detected within replications, 102,spots showed significant response to salt treatment compared to 0,mM,NaCl. We analyzed expression pattern of salt-responsive proteins using a hierarchical and two nonhierarchical (Fuzzy ART and SOM) statistical methods and concluded that Fuzzy ART is the superior method. Forty proteins of 12,different expression groups were analyzed using LC/MS/MS. Of these, 27,protein spots were identified including proteins involved in oxidative stress tolerance, glycinebetain synthesis, cytoskeleton remodeling, photosynthesis, ATP production, protein degradation, cyanide detoxification, and chaperone activities. The expression pattern of these proteins and their possible roles in the adaptation of S.,aegyptiaca to salinity is discussed. [source] Heat shock proteins as emerging therapeutic targetsBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2005Csaba Sõti Chaperones (stress proteins) are essential proteins to help the formation and maintenance of the proper conformation of other proteins and to promote cell survival after a large variety of environmental stresses. Therefore, normal chaperone function is a key factor for endogenous stress adaptation of several tissues. However, altered chaperone function has been associated with the development of several diseases; therefore, modulators of chaperone activities became a new and emerging field of drug development. Inhibition of the 90 kDa heat shock protein (Hsp)90 recently emerged as a very promising tool to combat various forms of cancer. On the other hand, the induction of the 70 kDa Hsp70 has been proved to be an efficient help in the recovery from a large number of diseases, such as, for example, ischemic heart disease, diabetes and neurodegeneration. Development of membrane-interacting drugs to modify specific membrane domains, thereby modulating heat shock response, may be of considerable therapeutic benefit as well. In this review, we give an overview of the therapeutic approaches and list some of the key questions of drug development in this novel and promising therapeutic approach. British Journal of Pharmacology (2005) 146, 769,780. doi:10.1038/sj.bjp.0706396 [source] Characterization of the glutamyl endopeptidase from Staphylococcus aureus expressed in Escherichia coliFEBS JOURNAL, Issue 3 2008Takayuki K. Nemoto V8 protease, a member of the glutamyl endopeptidase I family, of Staphylococcus aureus V8 strain (GluV8) is widely used for proteome analysis because of its unique substrate specificity and resistance to detergents. In this study, an Escherichia coli expression system for GluV8, as well as its homologue from Staphylococcus epidermidis (GluSE), was developed, and the roles of the prosegments and two specific amino acid residues, Val69 and Ser237, were investigated. C-terminal His6 -tagged proGluSE was successfully expressed from the full-length sequence as a soluble form. By contrast, GluV8 was poorly expressed by the system as a result of autodegradation; however, it was efficiently obtained by swapping its preprosegment with that of GluSE, or by the substitution of four residues in the GluV8 prosequence with those of GluSE. The purified proGluV8 was converted to the mature form in vitro by thermolysin treatment. The prosegment was essential for the suppression of proteolytic activity, as well as for the correct folding of GluV8, indicating its role as an intramolecular chaperone. Furthermore, the four amino acid residues at the C-terminus of the prosegment were sufficient for both of these roles. In vitro mutagenesis revealed that Ser237 was essential for proteolytic activity, and that Val69 was indispensable for the precise cleavage by thermolysin and was involved in the proteolytic reaction itself. This is the first study to express quantitatively GluV8 in E. coli, and to demonstrate explicitly the intramolecular chaperone activity of the prosegment of glutamyl endopeptidase I. [source] Functional characterization of artemin, a ferritin homolog synthesized in Artemia embryos during encystment and diapauseFEBS JOURNAL, Issue 4 2007Tao Chen Oviparously developing embryos of the crustacean Artemia franciscana encyst and enter diapause, exhibiting a level of stress tolerance seldom seen in metazoans. The extraordinary stress resistance of encysted Artemia embryos is thought to depend in part on the regulated synthesis of artemin, a ferritin superfamily member. The objective of this study was to better understand artemin function, and to this end the protein was synthesized in Escherichia coli and purified to apparent homogeneity. Purified artemin consisted of oligomers approximately 700 kDa in molecular mass that dissociated into monomers and a small number of dimers upon SDS/PAGE. Artemin inhibited heat-induced aggregation of citrate synthase in vitro, an activity characteristic of molecular chaperones and shown here to be shared by apoferritin and ferritin. This is the first report that apoferritin/ferritin may protect cells from stress other than by iron sequestration. Stably transfected mammalian cells synthesizing artemin were more resistant to heat and H2O2 than were cells transfected with vector only, actions also shared by molecular chaperones such as the small heat shock proteins. The data indicate that artemin is a structurally modified ferritin arising either from a common ancestor gene or by duplication of the ferritin gene. Divergence, including acquisition of a C-terminal peptide extension and ferroxidase center modification, eliminated iron sequestration, but chaperone activity was retained. Therefore, because artemin accumulates abundantly during development, it has the potential to protect embryos from stress during encystment and diapause without adversely affecting iron metabolism. [source] Protein disulfide isomerase family proteins involved in soybean protein biogenesisFEBS JOURNAL, Issue 3 2007Hiroyuki Wadahama Protein disulfide isomerase family proteins are known to play important roles in the folding of nascent polypeptides and the formation of disulfide bonds in the endoplasmic reticulum. In this study, we cloned two similar protein disulfide isomerase family genes from soybean leaf (Glycine max L. Merrill cv. Jack) mRNA by RT-PCR using forward and reverse primers designed from the expressed sequence tag clone sequences. The cDNA encodes a protein of either 364 or 362 amino acids, named GmPDIS-1 or GmPDIS-2, respectively. The nucleotide and amino acid sequence identities of GmPDIS-1 and GmPDIS-2 were 68% and 74%, respectively. Both proteins lack the C-terminal, endoplasmic reticulum-retrieval signal, KDEL. Recombinant proteins of both GmPDIS-1 and GmPDIS-2 were expressed in Escherichia coli as soluble folded proteins that showed both an oxidative refolding activity of denatured ribonuclease A and a chaperone activity. Their domain structures were identified as containing two thioredoxin-like domains, a and a,, and an ERp29c domain by peptide mapping with either trypsin or V8 protease. In cotyledon cells, both proteins were shown to distribute to the endoplasmic reticulum and protein storage vacuoles by confocal microscopy. Data from coimmunoprecipitation and crosslinking experiments suggested that GmPDIS-1 associates with proglycinin, a precursor of the seed storage protein glycinin, in the cotyledon. Levels of GmPDIS-1, but not of GmPDIS-2, were increased in cotyledons, where glycinin accumulates during seed development. GmPDIS-1, but not GmPDIS-2, was induced under endoplasmic reticulum-stress conditions. [source] R120G ,B-crystallin promotes the unfolding of reduced ,-lactalbumin and is inherently unstableFEBS JOURNAL, Issue 3 2005Teresa M. Treweek ,-Crystallin is the principal lens protein which, in addition to its structural role, also acts as a molecular chaperone, to prevent aggregation and precipitation of other lens proteins. One of its two subunits, ,B-crystallin, is also expressed in many nonlenticular tissues, and a natural missense mutation, R120G, has been associated with cataract and desmin-related myopathy, a disorder of skeletal muscles [Vicart P, Caron A, Guicheney P, Li Z, Prevost MC, Faure A, Chateau D, Chapon F, Tome F, Dupret JM, Paulin D & Fardeau M (1998) Nat Genet20, 92,95]. In the present study, real-time 1H-NMR spectroscopy showed that the ability of R120G ,B-crystallin to stabilize the partially folded, molten globule state of ,-lactalbumin was significantly reduced in comparison with wild-type ,B-crystallin. The mutant showed enhanced interaction with, and promoted unfolding of, reduced ,-lactalbumin, but showed limited chaperone activity for other target proteins. Using NMR spectroscopy, gel electrophoresis, and MS, we observed that, unlike the wild-type protein, R120G ,B-crystallin is intrinsically unstable in solution, with unfolding of the protein over time leading to aggregation and progressive truncation from the C-terminus. Light scattering, MS, and size-exclusion chromatography data indicated that R120G ,B-crystallin exists as a larger oligomer than wild-type ,B-crystallin, and its size increases with time. It is likely that removal of the positive charge from R120 of ,B-crystallin causes partial unfolding, increased exposure of hydrophobic regions, and enhances its susceptibility to proteolysis, thus reducing its solubility and promoting its aggregation and complexation with other proteins. These characteristics may explain the involvement of R120G ,B-crystallin with human disease states. [source] Chaperone activity of recombinant maize chloroplast protein synthesis elongation factor, EF-TuFEBS JOURNAL, Issue 18 2004Damodara Rao The protein synthesis elongation factor, EF-Tu, is a protein that carries aminoacyl-tRNA to the A-site of the ribosome during the elongation phase of protein synthesis. In maize (Zea mays L) this protein has been implicated in heat tolerance, and it has been hypothesized that EF-Tu confers heat tolerance by acting as a molecular chaperone and protecting heat-labile proteins from thermal aggregation and inactivation. In this study we investigated the effect of the recombinant precursor of maize EF-Tu (pre-EF-Tu) on thermal aggregation and inactivation of the heat-labile proteins, citrate synthase and malate dehydrogenase. The recombinant pre-EF-Tu was purified from Escherichia coli expressing this protein, and mass spectrometry confirmed that the isolated protein was indeed maize EF-Tu. The purified protein was capable of binding GDP (indicative of protein activity) and was stable at 45 °C, the highest temperature used in this study to test this protein for possible chaperone activity. Importantly, the recombinant maize pre-EF-Tu displayed chaperone activity. It protected citrate synthase and malate dehydrogenase from thermal aggregation and inactivation. To our knowledge, this is the first observation of chaperone activity by a plant/eukaryotic pre-EF-Tu protein. The results of this study support the hypothesis that maize EF-Tu plays a role in heat tolerance by acting as a molecular chaperone and protecting chloroplast proteins from thermal aggregation and inactivation. [source] Cytosolic chaperonin-containing t-complex polypeptide 1 changes the content of a particular subunit species concomitant with substrate binding and folding activities during the cell cycleFEBS JOURNAL, Issue 17 2001Shin-ichi Yokota The chaperonin-containing t-complex polypeptide 1 (CCT) is a cytosolic molecular chaperone composed of eight subunits that assists in the folding of actin, tubulin and other cytosolic proteins. We show here that the content of particular subunits of CCT within mammalian cells decreases concomitantly with the reduction of chaperone activity during cell cycle arrest at M phase. CCT recovers chaperone activity upon resumption of these subunits after release from M phase arrest or during arrest at S phase. The levels of ,, , and ,-1 subunits decreased more rapidly than the other subunits during M phase arrest by colcemid treatment and recovered after release from the arrest. Gel filtration chromatography or native (nondenaturing) PAGE analysis followed by immunoblotting indicated that the , and , subunit content in the 700- to 900-kDa CCT complex was appreciably lower in the M phase cells than in asynchronous cells. In vivo, the CCT complex of M-phase-arrested cells was found to bind lower amounts of tubulin than that of asynchronous cells. In vitro, the CCT complex of M phase-arrested cells was less active in binding and folding denatured actin than that of asynchronous cells. On the other hand, the CCT complex of asynchronous cells (a mixture of various phases of cell cycle) exhibited lower , and , subunit content and lower chaperone activity than that of S-phase-arrested cells obtained by excess thymidine treatment. In addition, turnover (synthesis and degradation) rates of the , and , subunits in vivo were more rapid than those of most other subunits. These results suggest that the content of , and , subunits of CCT reduces from the complete active complex in S phase cells to incomplete inactive complex in M phase cells. [source] Inactivation of oxidized and S -nitrosylated mitochondrial proteins in alcoholic fatty liver of rats,HEPATOLOGY, Issue 5 2006Kwan-Hoon Moon Increased oxidative/nitrosative stress is a major contributing factor to alcohol-mediated mitochondrial dysfunction. However, which mitochondrial proteins are oxidatively modified under alcohol-induced oxidative/nitrosative stress is poorly understood. The aim of this study was to systematically investigate oxidized and/or S -nitrosylated mitochondrial proteins and to use a biotin- N -maleimide probe to evaluate their inactivation in alcoholic fatty livers of rats. Binge or chronic alcohol exposure significantly elevated nitric oxide, inducible nitric oxide synthase, and ethanol-inducible CYP2E1. The biotin- N -maleimide-labeled oxidized and/or S -nitrosylated mitochondrial proteins from pair-fed controls or alcohol-fed rat livers were subsequently purified with streptavidin-agarose. The overall patterns of oxidized and/or S -nitrosylated proteins resolved by 2-dimensional polyacrylamide gel electrophoresis were very similar in the chronic and binge alcohol treatment groups. Seventy-nine proteins that displayed differential spot intensities from those of control rats were identified by mass spectrometry. These include mitochondrial aldehyde dehydrogenase 2 (ALDH2), ATP synthase, acyl-CoA dehydrogenase, 3-ketoacyl-CoA thiolase, and many proteins involved in chaperone activity, mitochondrial electron transfer, and ion transport. The activity of 3-ketoacyl-CoA thiolase involved in mitochondrial ,-oxidation of fatty acids was significantly inhibited in alcohol-exposed rat livers, consistent with hepatic fat accumulation, as determined by biochemical and histological analyses. Measurement of activity and immunoblot results showed that ALDH2 and ATP synthase were also inhibited through oxidative modification of their cysteine or tyrosine residues in alcoholic fatty livers of rats. In conclusion, our results help to explain the underlying mechanism for mitochondrial dysfunction and increased susceptibility to alcohol-mediated liver damage. (HEPATOLOGY 2006;44:1218,1230.) [source] Apurinic/apyrimidinic endonuclease 1, p53, and thioredoxin are linked in control of aging in C. elegansAGING CELL, Issue 3 2010Andreas Schlotterer Summary Deletions in mitochondrial DNA (mtDNA) accumulate during aging. Expression of the Caenorhabditis elegans apurinic/apyrimidinic endonuclease 1 (APE1) ortholog exo-3, involved in DNA repair, is reduced by 45% (P < 0.05) during aging of C. elegans. Suppression of exo-3 by treatment with RNAi resulted in a threefold increase in mtDNA deletions (P < 0.05), twofold enhanced generation of reactive oxygen species (ROS) (P < 0.01), distortion of the structural integrity of the nervous system, reduction of head motility by 43% (P < 0.01) and whole animal motility by 38% (P < 0.05). Suppression of exo-3 significantly reduced life span: mean life span decreased from 18.5 ± 0.4 to 15.4 ± 0.1 days (P < 0.001) and maximum life span from 25.9 ± 0.4 to 23.2 ± 0.1 days (P = 0.001). Additional treatment of exo-3 -suppressed animals with a mitochondrial uncoupler decreased ROS levels, reduced neuronal damage, and increased motility and life span. Additional suppression of the C. elegans p53 ortholog cep-1 in exo-3 RNAi-treated animals similarly decreased ROS levels, preserved neuronal integrity, and increased motility and life span. In wild-type animals, suppression of cep-1, involved in downregulation of exo-3, increased expression of exo-3 without a significant effect on ROS levels, preserved neuronal integrity, and increased motility and life span. Suppression of the C. elegans thioredoxin orthologs trx-1 and trx-2, involved in the redox chaperone activity of exo-3, overrides the protective effect of cep-1 RNAi treatment on neuronal integrity, neuronal function, mean and maximum life span. These results show that APE1/EXO-3, p53/CEP-1, and thioredoxin affect each other and that these interactions determine aging as well as neuronal structure and function. [source] Structure, function, property, and role in neurologic diseases and other diseases of the sHsp22JOURNAL OF NEUROSCIENCE RESEARCH, Issue 10 2007Zhiping Hu Abstract Small heat shock proteins are members of the heat shock proteins family. They share important identical features: 1) they form the conserved structure ,,-crystallin domain' with about 80,100 residues in the C-terminal part of the proteins; 2) they have monomeric molecular masses ranging in 12,43 kDa; 3) they associate into large oligomers consisting in many cases of subunits; 4) they increase expression under stress conditions; 5) they exhibit a highly dynamic structure; and 6) they play a chaperone-like role. Hsp22 (also known as HspB8, H11, and E2IG1) retains the structural motif of the ,,-crystallin' family of Hsps and is a member of the superfamily of sHsps. Hsp22 displays chaperone activity, autokinase activity, and trigger or block apoptosis activity. It differs from canonical family members existing as a monomer. A decrease in the HspB8 activity may contribute to the development of some neurologic diseases and others. © 2007 Wiley-Liss, Inc. [source] Molecular dynamic simulations of nanomechanic chaperone peptide and effects of in silico His mutations on nanostructured functionJOURNAL OF PEPTIDE SCIENCE, Issue 11 2008Abolfazl Barzegar Abstract The nanoscale peptide YSGVCHTDLHAWHGDWPLPVK exhibits molecular chaperone activity and prevents protein aggregation under chemical and/or thermal stress. Here, His mutations of this peptide and their impact on chaperone activity were evaluated using theoretical techniques. Molecular dynamic (MD) simulations with simulated annealing (SA) of different mutant nanopeptides were employed to determine the contribution of the scaffolding His residues (H45, H49, H52), when mutated to Pro, on chaperone action in vitro. The in silico mutations of His residues to Pro (H45P, H49P, H52P) revealed loss of secondary ordered strand structure. However, a small part of the strand conformation was formed in the middle region of the native chaperone peptide. The His-to-Pro mutations resulted in decreased gyration radius (Rg) values and surface accessibility of the mutant peptides under the simulation times. The invariant dihedral angle (,) values and the disrupting effects of the Pro residues indicated the coil conformation of mutant peptides. The failure of the chaperone-like action in the Pro mutant peptides was consistent with their decreased effective accessible surfaces. The high variation of , value for His residues in native chaperone peptide leads to high flexibility, such as a minichaperone acting as a nanomachine at the molecular level. Our findings demonstrate that the peptide strand conformation motif with high flexibility at nanoscale is critical for chaperone activity. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] Escherichia coli Hsp31 functions as a holding chaperone that cooperates with the DnaK-DnaJ-GrpE system in the management of protein misfolding under severe stress conditionsMOLECULAR MICROBIOLOGY, Issue 3 2004Mirna Mujacic Summary Escherichia coli Hsp31 is a homodimeric protein that exhibits chaperone activity in vitro and is a representative member of a recently recognized family of heat shock proteins (Hsps). To gain insights on Hsp31 cellular function, we deleted the hchA gene from the MC4100 chromosome and combined the resulting null allele with lesions in other cytoplasmic chaperones. Although the hchA mutant only exhibited growth defects when cultivated at 48°C, loss of Hsp31 had a strong deleterious effect on the ability of cells to survive and recover from transient exposure to 50°C, and led to the enhanced aggregation of a subset of host proteins at this temperature. The absence of Hsp31 did not significantly affect the ability of the ClpB-DnaK-DnaJ-GrpE system to clear thermally aggregated proteins at 30°C suggesting that Hsp31 does not possess disaggregase activity. Although it had no effect on the growth of groES30, ,clpB or ,ibpAB cells at high temperatures, the hchA deletion aggravated the temperature sensitive phenotype of dnaK756 and grpE280 mutants and led to increased aggregation in stressed dnaK756 cells. On the basis of biochemical, structural and genetic data, we propose that Hsp31 acts as a modified holding chaperone that captures early unfolding intermediates under prolonged conditions of severe stress and releases them when cells return to physiological conditions. This additional line of defence would complement the roles of DnaK-DnaJ-GrpE, ClpB and IbpB in the management of thermally induced cellular protein misfolding. [source] Not all J domains are created equal: Implications for the specificity of Hsp40,Hsp70 interactionsPROTEIN SCIENCE, Issue 7 2005Fritha Hennessy Abstract Heat shock protein 40s (Hsp40s) and heat shock protein 70s (Hsp70s) form chaperone partnerships that are key components of cellular chaperone networks involved in facilitating the correct folding of a broad range of client proteins. While the Hsp40 family of proteins is highly diverse with multiple forms occurring in any particular cell or compartment, all its members are characterized by a J domain that directs their interaction with a partner Hsp70. Specific Hsp40,Hsp70 chaperone partnerships have been identified that are dedicated to the correct folding of distinct subsets of client proteins. The elucidation of the mechanism by which these specific Hsp40,Hsp70 partnerships are formed will greatly enhance our understanding of the way in which chaperone pathways are integrated into finely regulated protein folding networks. From in silico analyses, domain swapping and rational protein engineering experiments, evidence has accumulated that indicates that J domains contain key specificity determinants. This review will critically discuss the current understanding of the structural features of J domains that determine the specificity of interaction between Hsp40 proteins and their partner Hsp70s. We also propose a model in which the J domain is able to integrate specificity and chaperone activity. [source] Structures of and interactions between domains of trigger factor from Thermotoga maritimaACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2007Erik Martinez-Hackert Trigger factor (TF) is a eubacterial chaperone that associates with ribosomes at the peptide-exit tunnel and also occurs in excess free in the cytosol. TF is a three-domain protein that appears to exist in a dynamic equilibrium of oligomerization states and interdomain conformations. X-ray crystallography and chemical cross-linking were used to study the roles of the N- and C-terminal domains of Thermotoga maritima TF in TF oligomerization and chaperone activity. The structural conservation of both the N- and C-terminal TF domains was unambiguously established. The biochemical and crystallographic data reveal a tendency for these domains to partake in diverse and apparently nonspecific protein,protein interactions. It is found that the T. maritima and Escherichia coli TF surfaces lack evident exposed hydrophobic patches. Taken together, these data suggest that TF chaperones could interact with nascent proteins via hydrophilic surfaces. [source] RIC-3: a nicotinic acetylcholine receptor chaperoneBRITISH JOURNAL OF PHARMACOLOGY, Issue S1 2008N S Millar RIC-3 is a transmembrane protein which acts as a molecular chaperone of nicotinic acetylcholine receptors (nAChRs). For some nAChR subtypes (such as homomeric ,7 neuronal nAChRs), RIC-3 is required for efficient receptor folding, assembly and functional expression. In contrast, for other nAChR subtypes (such as heteromeric ,4,2 neuronal nAChRs) there have been reports that RIC-3 can both enhance and reduce levels of functional expression. There is also evidence that RIC-3 can modulate maturation of the closely related 5-hydroxytryptamine (5-HT) receptor (5-HT3R). As with heteromeric nAChRs, apparently contradictory results have been reported for the influence of RIC-3 on 5-HT3R maturation in different expression systems. Recent evidence indicates that these differences in RIC-3 chaperone activity may be influenced by the host cell, suggesting that other proteins may play an important role in modulating the effects of RIC-3 as a chaperone. RIC-3 was originally identified in the nematode Caenorhabditis elegans as the protein encoded by the gene ric-3 (resistance to inhibitors of cholinesterase) and has subsequently been cloned and characterized from mammalian and insect species. This review provides a brief history of RIC-3; from the identification of the ric-3 gene in C. elegans in 1995 to the more recent demonstration of its activity as a nAChR chaperone. British Journal of Pharmacology (2008) 153, S177,S183; doi:10.1038/sj.bjp.0707661; published online 4 February 2008 [source] Structure-Based and in,silico Design of Hsp90 InhibitorsCHEMMEDCHEM, Issue 9 2009Miriam Sgobba Dr. Abstract The molecular chaperone Hsp90 is responsible for activation and stabilization of several oncoproteins in cancer cells, and has emerged as an important target in cancer treatment because of this pivotal role. In recent years, interests have arisen around structure-based design of small molecules aimed at inhibiting the chaperone activity of Hsp90. In this review, we illustrate the recent advances in structure-based and in,silico strategies aimed at discovering and optimizing Hsp90 inhibitors. [source] | ||||||||||||||||