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)

Expression of the aconitase (citB) gene of Bacillus subtilis is subject to catabolite repression in cells grown in minimal media. In nutrient broth medium, citB expression is low in growing cells but is induced when cells enter sporulation. A 600-base-pair DNA fragment that extends from positions -400 through +200, relative to the transcription start site, was shown to include all of the cis-acting sequences necessary for catabolite repression and sporulation-associated regulation. This was demonstrated by fusing this DNA fragment to the Escherichia coli lacZ gene, integrating the fusion in the amyE locus of the B. subtilis chromosome, and measuring the regulation of expression of beta-galactosidase. By creating a series of deletions from either end of the 600-base-pair fragment, it was possible to define a target for catabolite repression; at least part of this target lies within the sequence between positions -84 and -68. DNA fragments that included positions -84 through +36, when carried on high-copy plasmids, caused derepression of aconitase synthesis, as if a negative regulator were being titrated. The same plasmids caused derepression of citrate synthase activity as well. Deletion of the sequence between positions -84 and -67 abolished this titration effect for both enzymes. Mutations that altered the target for catabolite repression also affected the inducibility of citB at the onset of sporulation, at least when sporulation was induced by the addition of decoyinine, an inhibitor of guanine nucleotide synthesis. When sporulation was induced by exhaustion of nutrient broth, there was no detectable difference in expression of citB-lacZ fusions whether or not they had the citB sequence from positions -84 to -67, suggesting that the mechanisms of regulation of citB in minimal medium and nutrient broth are different.
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PMID:A target for carbon source-dependent negative regulation of the citB promoter of Bacillus subtilis. 210 5

The citB of Bacillus subtilis codes for aconitase (D. W. Dingman and A. L. Sonenshein, J. Bacteriol. 169:3060-3065). By direct measurements of citB mRNA levels and by measurements of beta-galactosidase activity in a strain carrying a citB-lacZ fusion, we have examined the expression of citB during growth and sporulation. When cells were grown in nutrient broth sporulation medium, citB mRNA appeared in mid- to late-exponential phase and disappeared by the second hour of sporulation. This timing corresponded closely to the kinetics of appearance of aconitase enzyme activity. Decoyinine, a compound that induces sporulation in a defined medium, caused a rapid simultaneous increase in aconitase activity and citB transcription. After decoyinine addition, the rate of increase in aconitase activity in a 2-ketoglutarate dehydrogenase (citK) mutant and in a citrate synthase (citA) mutant was significantly less than in an isogenic wild-type strain. This is apparently due to a failure to deplete 2-ketoglutarate and accumulate citrate. These metabolites might act as negative and positive effectors of citB expression, respectively. Mutations known to block sporulation at an early stage (spo0H and spo0B) had no appreciable effect on citB expression or aconitase activity. These results suggest that appearance of aconitase is stimulated by conditions that induce sporulation but is independent of certain gene products thought to act at an early stage of sporulation.
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PMID:Relationship between aconitase gene expression and sporulation in Bacillus subtilis. 311 Jan 34

Acetohydroxy acid synthetase, which is sensitive to catabolite repression in wild-type Escherichia coli B, was relatively resistant to this control in a streptomycin-dependent mutant. The streptomycin-dependent mutant was found to be inducible for beta-galactosidase in the presence of glucose, although repression of beta-galactosidase by glucose occurred under experimental conditions where growth of the streptomycin-dependent mutant was limited. Additional glucose-sensitive enzymes of wild-type E. coli B (citrate synthase, fumarase, aconitase and isocitrate dehydrogenase) were found to be insensitive to the carbon source in streptomycin-dependent mutants: these enzymes were formed by streptomycin-dependent E. coli B in equivalent quantities when either glucose or glycerol was the carbon source. Two enzymes, glucokinase and glucose 6-phosphate dehydrogenase, that are glucose-insensitive in wild-type E. coli B were formed in equivalent quantity on glucose or glycerol in both streptomycin-sensitive and streptomycin-dependent E. coli B. The results indicate a general decrease or relaxation of catabolite repression in the streptomycin-dependent mutant. The yield of streptomycin-dependent cells from glucose was one-third less than that of the streptomycin-sensitive strain. We conclude that the decreased efficiency of glucose utilization in streptomycin-dependent E. coli B is responsible for the relaxation of catabolite repression in this mutant.
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PMID:Relaxation of catabolite repression in streptomycin-dependent Escherichia coli. 497 19

Muscle hypertrophy was induced in the soleus muscle of young rats by tenotomy of the gastrocnemius and plantaris muscles. Three and 7 days afterwards the sciatic nerve was sectioned. The loss of weight of muscles subjected to this combined procedure three days after denervation was 30-40%. Lysosomal enzyme activities (acid phosphatase, alpha-glucosidase, beta-galactosidase and N-acetyl-beta-D-glucosaminidase) and energy enzyme activities (lactate dehydrogenase, LDH, triose-3-phosphate dehydrogenase, TPDH , D-hexokinase, HK and citrate synthase, CS) were determined 3 days after denervation, 3, 7 and 10 days after hypertrophy had been induced and 3 days after denervation of hypertrophying muscles on day 3 and 7. Normal non-operated rats of corresponding body weight served as controls and their enzyme activities were estimated on the same day. In the course of muscle hypertrophy, the 4 lysosomal enzyme activities increased progressively. Although 3 days' denervation of control muscles did not alter lysosomal enzyme activities, denervation of hypertrophying muscles greatly enhanced the activity of these enzymes. Enzymes of energy metabolism were affected to a lesser degree. The results suggest that denervation of hypertrophying muscles causes more extreme changes in muscle weight and lysosomal enzyme activities than denervation alone. The possible implications of this finding are discussed in relation to the rapid atrophy.
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PMID:Lysosomal and energy enzyme activities in hypertrophied rat soleus muscle after denervation. 671 25

We propose a method to study multienzyme complex formation in vitro based on nondenaturing agarose gel electrophoresis. The enzymes with different isoelectric points (pI) were loaded at the opposite ends of the same lane of agarose gel and electrophoresis was performed at a pH value intermediate between their pI's. In cases where a complex of the enzymes was formed, an additional protein band of low electrophoretic mobility was found corresponding to the point where they crossed on the gel. This band contained both enzyme activities. The method was used to demonstrate association between two enzymes of the mitochondrial citric acid cycle, malate dehydrogenase and citrate synthase, and between the lysosomal hydrolases, beta-galactosidase and cathepsin A. Relative proportions of free and bound enzymes after electrophoresis suggest that interaction between the mitochondrial enzymes is relatively weak compared to that of lysosomal hydrolases. Microdensitometric scanning of countermigration electrophoresis gels was used to determine the stoichiometry of components in the complex.
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PMID:Demonstration of enzyme associations by countermigration electrophoresis in agarose gel. 808 91

Although calmodulin is known to be a component of the Hsp70/Hsp90 multichaperone complex, the functional role of the protein remains uncertain. In this study, we have identified S100A1, but not calmodulin or other S100 proteins, as a potent molecular chaperone and a new member of the multichaperone complex. Glutathione S-transferase pull-down assays and co-immunoprecipitation experiments indicated the formation of stable complexes between S100A1 and Hsp90, Hsp70, FKBP52, and CyP40 both in vitro and in mammalian cells. S100A1 potently protected citrate synthase, aldolase, glyceraldehyde-3-phosphate dehydrogenase, and rhodanese from heat-induced aggregation and suppressed the aggregation of chemically denatured rhodanese and citrate synthase during the refolding pathway. In addition, S100A1 suppressed the heat-induced inactivation of citrate synthase activity, similar to that for Hsp90 and p23. The chaperone activity of S100A1 was antagonized by calmodulin antagonists, such as fluphenazine and prenylamine, that is, indeed an intrinsic function of the protein. The overexpression of S100A1 in COS-7 cells protected transiently expressed firefly luciferase and Escherichia coli beta-galactosidase from inactivation during heat shock. The results demonstrate a novel physiological function for S100A1 and bring us closer to a comprehensive understanding of the molecular mechanisms of the Hsp70/Hsp90 multichaperone complex.
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PMID:S100A1 is a novel molecular chaperone and a member of the Hsp70/Hsp90 multichaperone complex. 1463 89

We used preS2-S'-beta-galactosidase, a three-domain fusion protein that aggregates extensively at 43 degrees C in the cytoplasm of Escherichia coli, to search for multicopy suppressors of protein aggregation and inclusion body formation and took advantage of the known differential solubility of preS2-S'-beta-galactosidase at 37 and 43 degrees C to develop a selection procedure for the gene products that would prevent its aggregation in vivo at 43 degrees C. First, we demonstrate that the differential solubility of preS2-S'-beta-galactosidase results in a lactose-positive phenotype at 37 degrees C as opposed to a lactose-negative phenotype at 43 degrees C. We searched for multicopy suppressors of preS2-S'-beta-galactosidase aggregation by selecting pink lactose-positive colonies on a background of white lactose-negative colonies at 43 degrees C after transformation of bacteria with an E. coli gene bank. We discovered that protein isoaspartate methyltransferase (PIMT) is a multicopy suppressor of preS2-S'-beta-galactosidase aggregation at 43 degrees C. Overexpression of PIMT reduces the amount of preS2-S'-beta-galactosidase found in inclusion bodies at 43 degrees C and increases its amount in soluble fractions. It reduces the level of isoaspartate formation in preS2-S'-beta-galactosidase and increases its thermal stability in E. coli crude extracts without increasing the thermostability of a control protein, citrate synthase, in the same extracts. We could not detect any induction of the heat shock response resulting from PIMT overexpression, as judged from amounts of DnaK and GroEL, which were similar in the PIMT-overproducing and control strains. These results suggest that PIMT might be overburdened in some physiological conditions and that its overproduction may be beneficial in conditions in which protein aggregation occurs, for example, during biotechnological protein overproduction or in protein aggregation diseases.
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PMID:Protein isoaspartate methyltransferase is a multicopy suppressor of protein aggregation in Escherichia coli. 1568 2