Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Beta-synuclein exhibits high sequence homology and structural similarity with alpha-synuclein, a protein implicated in the pathogenesis of Parkinson's disease. We investigated the chaperone function of beta-synuclein and its anti-fibrillar activity in comparison with alpha-synuclein. beta-Synuclein suppressed the heat-induced aggregation of aldolase, alcohol dehydrogenase, and citrate synthase, and its anti-aggregative activity was remarkably higher than that of alpha-synuclein. Heat-induced inactivation of citrate synthase was significantly protected by beta-synuclein. Moreover, beta-synuclein inhibited the amyloid formation of both Abeta(1-40) and alpha-synuclein. It is, therefore, suggested that beta-synuclein can prevent abnormal protein aggregations more effectively than alpha-synuclein by acting as a molecular chaperone.
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PMID:Beta-synuclein exhibits chaperone activity more efficiently than alpha-synuclein. 1547 47

4,4'-Dianilino-1,1'-binaphthyl-5,5'-sulfonate (bis-ANS) and 1-anilinonaphthalene-8-sulfonate (ANS) are hydrophobic probes that are widely used in protein folding studies, using their capacity to bind to hydrophobic regions of partially unfolded proteins and in turn leading to an increase in fluorescence. Here we reveal a novel chaperone-like activity for bis-ANS, which acted as a highly effective inhibitor for the thermal- or chemical-induced aggregation of alcohol dehydrogenase, insulin or the whole cell extract of Escherichia coli, with ANS showing a much weaker effect. The studies to elucidate the mechanism underlying this activity show that bis-ANS is able to form stable soluble aggregates with the denaturing proteins and dramatically increase its fluorescence intensity upon incubation with aggregation-prone proteins. Moreover, we found that bis-ANS is able to prevent the heat inactivation of citrate synthase. These observations suggest that bis-ANS is able to block the exposed hydrophobic surfaces to suppress protein aggregation, acting in a way similar to what small heat shock proteins (one sub-class of molecular chaperones) do. The data presented here, together with the report that bis-ANS was able to suppress the amyloid formation of the prion peptide [J. Biol. Chem. 279 (2004) 5346], suggest that this molecule may be used as a potential protein stabilizer in addition to its current application as a hydrophobic probe.
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PMID:4,4'-Dianilino-1,1'-binaphthyl-5,5'-sulfonate, a novel molecule having chaperone-like activity. 1575 65

Protein pin arrays identified seven interactive sequences for chaperone activity in human alphaB crystallin using natural lens proteins, beta(H) crystallin and gammaD crystallin, and in vitro chaperone target proteins, alcohol dehydrogenase and citrate synthase. The N-terminal domain contained two interactive sequences, (9)WIRRPFFPFHSP(20) and (43)SLSPFYLRPPSFLRAP(58). The alpha crystallin core domain contained four interactive sequences, (75)FSVNLDVK(82) (beta3), (113)FISREFHR(120), (131)LTITSSLS(138) (beta8), and (141)GVLTVNGP(148) (beta9). The C-terminal domain contained one interactive sequence, (157)RTIPITRE(164), that included the highly conserved I-X-I/V motif. Two interactive sequences, (73)DRFSVNLDVKHFS(85) and (131)LTITSSLSDGV(141), belonging to the alpha crystallin core domain were synthesized as peptides and assayed for chaperone activity in vitro. Both synthesized peptides inhibited the thermal aggregation of beta(H) crystallin, alcohol dehydrogenase, and citrate synthase in vitro. Five of the seven chaperone sequences identified by the pin arrays overlapped with sequences identified previously as sequences for subunit-subunit interactions in human alphaB crystallin. The results suggested that interactive sequences in human alphaB crystallin have dual roles in subunit-subunit assembly and chaperone activity.
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PMID:Interactive domains for chaperone activity in the small heat shock protein, human alphaB crystallin. 1627 33

Knowledge of the interactive domains on the surface of small heat shock proteins (sHSPs) is necessary for understanding the assembly of complexes and the activity as molecular chaperones. The primary sequences of 26 sHSP molecular chaperones were aligned and compared. In the interactive beta3 sequence, 73DRFSVNLDVKHFS85 of human alphaB crystallin, Ser-76, Asn-78, Lys-82, and His-83 were identified as nonconserved residues on the exposed surface of the alpha crystallin core domain. Site-directed mutagenesis produced the mutant alphaB crystallins: S76E, N78G, K82Q, and H83F. Domain swapping with homologous beta3 sequences, 32EKFEVGLDVQFFT44 from Caenorhabditis elegans sHSP12.2 or 69DKFVIFLDVKHFS81 from alphaA crystallin, resulted in the mutant alphaB crystallins, CE1 and alphaA1, respectively. Decreased chaperone activity was observed with the point mutants N78G, K82Q, and H83F and with the mutant, CE1, in aggregation assays using betaL crystallin, alcohol dehydrogenase (ADH), or citrate synthase (CS). The S76E mutant had minimal effect on chaperone activity, and domain swapping with alphaA crystallin had no effect on chaperone activity. The mutations that resulted in altered chaperone activity, produced minimal modification to the secondary, tertiary, and quaternary structure of human alphaB crystallin as determined by ultraviolet circular dichroism spectroscopy, chymotrypsin proteolysis, and size exclusion chromatography. Chaperone activity was influenced by the amount of unfolding of the target proteins and independent of complex size. The results characterized the importance of the exposed side chains of Glu-78, Lys-82, and His-83 in the interactive beta3 sequence of the alpha crystallin core domain in alphaB crystallin for chaperone function.
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PMID:The function of the beta3 interactive domain in the small heat shock protein and molecular chaperone, human alphaB crystallin. 1681 25

The functional importance of the beta8 sequence ((131)LTITSSLS(138)), which is on the surface of the alpha crystallin core domain of human alphaB crystallin, was evaluated using site-directed mutagenesis. Ultraviolet circular dichroism determined that mutating the surface-exposed, nonconserved residues, Leu-131, Thr-132, Thr-134, Ser-135, Ser-136, and Ser-138 individually or in combination (alphaAbeta8 and CEbeta8), had no measurable effect on secondary and tertiary structure. Size exclusion chromatography determined the size of the complexes formed by the beta8 mutants to be 6-8 subunits larger than wt alphaB crystallin. In chaperone assays, the protective effect of the L131S, T132A, and S135C mutants of the beta8 sequence was similar to wt alphaB crystallin when beta(L) crystallin and alcohol dehydrogenase were the chaperone substrates and decreased to 66% when citrate synthase was the chaperone substrate. In contrast, the chaperone activity for all three substrates was dramatically reduced for the T134K, S138A, S136H, and CEbeta8 mutants. The prominent location of Thr-134, Ser-136, and Ser-138 on the exposed surface of the alpha crystallin core domain could account for the effect on complex assembly and chaperone activity. Modulation of chaperone activity by the exposed residues of the beta8 sequence in the alpha crystallin core domain was independent of complex size. The results established the beta3-beta8-beta9 surface of the alpha crystallin core domain as an interface for complex assembly and chaperone activity.
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PMID:Structure-based analysis of the beta8 interactive sequence of human alphaB crystallin. 1689 88

The functions of the interactive sequences in human alphaB crystallin that are involved in chaperone activity and complex assembly of small heat shock proteins need to be characterized to understand the mechanisms of action on unfolding and misfolding proteins. Protein pin arrays identified the hydrophobic N-terminal sequence (41STSLSPFYLRPPSFLRAP58) and the polar C-terminal sequence (155PERTIPITREE165) as interactive domains in human alphaB crystallin, which were then deleted to evaluate their importance in complex assembly and chaperone activity. Size exclusion chromatography determined that the complexes formed by the deletion mutants, Delta41-58 and Delta155-165, were larger and more polydisperse than the wild-type (wt) alphaB crystallin complex. In chaperone assays, the Delta41-58 mutant was as effective as wt alphaB crystallin in protecting partially unfolded betaL crystallin and alcohol dehydrogenase (ADH) and significantly less effective than wt alphaB crystallin in protecting unfolded citrate synthase (CS) from aggregation. Chaperone activity did not correlate with complex size but corresponded with the amount of substrate protein unfolding. The results confirmed the importance of N-terminal residues 41-58 in selective interactions with completely unfolded substrates. Poor solubility and limited or no chaperone activity for the three substrates characterized the Delta155-165 deletion mutant, which demonstrated the importance of C-terminal residues 155-165 in maintaining the solubility of unfolded substrates in a manner independent of the amount of substrate protein unfolding. The results presented in this report established that interactive domains in the N- and C-termini of human alphaB crystallin are important for the recognition, selection, and solubility of unfolding substrate proteins.
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PMID:N- and C-Terminal motifs in human alphaB crystallin play an important role in the recognition, selection, and solubilization of substrates. 1710 3

The cytoskeleton has a unique property such that changes of conformation result in polymerization into a filamentous form. alphaB-Crystallin, a small heat shock protein (sHsp), has chaperone activities for various substrates, including proteins constituting the cytoskeleton, such as actin; intermediate filament; and tubulin. However, it is not clear whether the "alpha-crystallin domain" common to sHsps also has chaperone activity for the protein cytoskeleton. To investigate the possibility that the C-terminal alpha-crystallin domain of alpha-crystallin has the aggregation-preventing ability for tubulin, we constructed an N-terminal domain deletion mutant of alphaB-crystallin. We characterized its structural properties and chaperone activities. Far-ultraviolet (UV) circular dichroism measurements showed that secondary structure in the alpha-crystallin domain of the deletion mutant is maintained. Ultracentrifuge analysis of molecular masses indicated that the deletion mutant formed smaller oligomers than did the full-length protein. Chaperone activity assays demonstrated that the N-terminal domain deletion mutant suppressed heat-induced aggregation of tubulin well. Comparison of chaperone activities for 2 other substrates (citrate synthase and alcohol dehydrogenase) showed that it was less effective in the suppression of their aggregation. These results show that alphaB-crystallin recognizes a variety of substrates and especially that alpha-crystallin domain binds free cytoskeletal proteins. We suggest that this feature would be advantageous in its functional role of holding or folding multiple proteins denatured simultaneously under stress conditions.
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PMID:Analysis of the alphaB-crystallin domain responsible for inhibiting tubulin aggregation. 1768 95

During aging, human lens proteins undergo several post-translational modifications, one of which is glycation. This process leads to the formation of advanced glycation end products (AGEs) which accumulate with time possibly leading to the formation of cataract. alphaB-Crystallin, a predominant protein in the lens, is a member of the small heat shock proteins (sHSPs) which are a ubiquitous class of molecular chaperones that interact with partially denatured proteins to prevent aggregation. This chaperone function is considered to be vital for the maintenance of lens transparency and in the prevention of cataract. In the present study, we introduced an analog of the advanced glycation end product, OP-lysine, at the 90th position of a mutated human alphaB-crystallin (K90C) by covalent modification of the cysteine residue with N-(2-bromoethyl)-3-oxidopyridinium hydrobromide. The AGE-modified K90C-alphaB-crystallin is termed as K90C-OP. We compared the structural and functional properties of K90C-OP with the original K90C mutant, with K90C chemically modified back to a lysine analog (K90C-AE), and with wild-type human alphaB-crystallin. Modified K90C-OP showed decreased intrinsic tryptophan fluorescence and bis-ANS binding without significant alterations in either the secondary, tertiary, or quaternary structure. K90C-OP, however, exhibited a reduced efficiency in the chaperoning ability with alcohol dehydrogenase, insulin, and citrate synthase as substrates compared to the other alpha-crystallin proteins. Therefore, introduction of a single AGE near the chaperone site of human alphaB-crystallin can alter the chaperoning ability of the protein with only minor changes in the local environment of the protein.
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PMID:Effect of a single AGE modification on the structure and chaperone activity of human alphaB-crystallin. 1802 13

ERD10 and ERD14 (for early response to dehydration) proteins are members of the dehydrin family that accumulate in response to abiotic environmental stresses, such as high salinity, drought, and low temperature, in Arabidopsis (Arabidopsis thaliana). Whereas these proteins protect cells against the consequences of dehydration, the exact mode(s) of their action remains poorly understood. Here, detailed evidence is provided that ERD10 and ERD14 belong to the family of intrinsically disordered proteins, and it is shown in various assays that they act as chaperones in vitro. ERD10 and ERD14 are able to prevent the heat-induced aggregation and/or inactivation of various substrates, such as lysozyme, alcohol dehydrogenase, firefly luciferase, and citrate synthase. It is also demonstrated that ERD10 and ERD14 bind to acidic phospholipid vesicles without significantly affecting membrane fluidity. Membrane binding is strongly influenced by ionic strength. Our results show that these intrinsically disordered proteins have chaperone activity of rather wide substrate specificity and that they interact with phospholipid vesicles through electrostatic forces. We suggest that these findings provide the rationale for the mechanism of how these proteins avert the adverse effects of dehydration stresses.
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PMID:Chaperone activity of ERD10 and ERD14, two disordered stress-related plant proteins. 1835 42

In vitro chaperone-like activity of the serpin family member and plasma acute-phase component human alpha(1)-antitrypsin (AAT) has been shown for the first time. Results of light-scattering experiments demonstrated that AAT efficiently inhibits both heat- and chemical-induced aggregation of various test proteins including alcohol dehydrogenase, aldolase, carbonic anhydrase, catalase, citrate synthase, enolase, glutathione S-transferase, l-lactate dehydrogenase, and beta(L)-crystallin. The results suggest that the unique metastable serpin architecture enables dual function, protease inhibiton as well as chaperone activity and highlight the serpin superfamily as a possible source of additional intra- and extracellular chaperones (e.g. alpha(1)-antichymotrypsin). The present finding is surprising in the light of the well-known role of mutated forms of AAT and other serpins in the pathogenesis of diseases called serpinopathies that featured with aberrant conformational transitions and consequent self-aggregation of serpin proteins.
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PMID:Inhibition of heat- and chemical-induced aggregation of various proteins reveals chaperone-like activity of the acute-phase component and serine protease inhibitor human alpha(1)-antitrypsin. 2011 85


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