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:4.1.99.3 (PRE)
1,923 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Yeast DNA photolyase, purified by affinity chromatography, ran as a single component when analyzed by either electrophoresis on polyacrylamide gradient gels or by sedimentation velocity through 5-20% sucrose gradients containing 0.4 M KCl, and, therefore, was considered homogeneous. The molecular weights of photolyase, determined by these methods, were 130000 and 136000, respectively. When the enzyme was examined by electrophoresis on sodium dodecyl sulfate polyacrylamide gradient gels, it dissociated into two bands whole molecular weights were 60000 and 85000. After the enzyme was sedimented through sucrose gradients in the presence of 1.0 M KCl, two absorbance maxima, which corresponded to polypeptides of 54000 and 82500, were found in the fractions collected. Thus, the enzyme consists of two dissimilar subunits. When the two fractions that exhibited maximal absorbance were mixed together, a time-dependent increase in activity occurred, demonstrating that active enzyme could be reconstituted from these subunits. Analysis of sucrose gradients containing 1.0 M salt for photolyase activity showed that it was present exclusively in the region of the gradient corresponding to 68200 in agreement with a previous report (J. Cook and T. Worthy (1972), Biochemistry 11, 388). These active fractions were found in the overlap region between the two subunits, and their activity was attributed to reconstitution of the enzyme during the assay.
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PMID:Yeast DNA photolyase: molecular weight, subunit structure, and reconstruction of active enzyme from its subunits. 110 68

Thirteen patients undergoing cardiac surgery were studied to examine whether beta-adrenergic desensitization occurs in the perioperative period surrounding cardiac surgery, using peripheral blood lymphocytes as a model. Lymphocytes were isolated before induction of anesthesia (PRE) and on the morning of the first postoperative day (POST). Cyclic adenosine monophosphate (cAMP) production from the lymphocytes was assayed in the untreated (BASAL) state, and after treatment with 5 microM isoproterenol, 10 microM prostaglandin E1, or 20 mM sodium fluoride with 10 microM AlCl3 (NaF). All cAMP values are reported as picomoles per 10(6) cells, mean +/- SEM. BASAL cAMP production did not change significantly between the PRE and POST samples (PRE, 1.2 +/- 0.1; POST, 1.0 +/- 0.1). Isoproterenol-stimulated cAMP was significantly lower postoperatively (PRE, 8.36 +/- 0.9; POST, 5.1 +/- 0.5; P less than 0.005). Prostaglandin E1-stimulated cAMP did not change (PRE, 21.7 +/- 2.4; POST, 25.3 +/- 2.5), and NaF-stimulated cAMP was increased postoperatively (PRE, 8.8 +/- 1.6; POST, 14.3 +/- 2.0; P less than 0.05). These findings suggest that cardiac surgery and/or cardiopulmonary bypass results in significant desensitization of the beta-adrenergic receptor/adenylate cyclase system of lymphocytes, which may parallel changes in the adrenergic response of other organ systems.
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PMID:Cardiac surgery causes desensitization of the beta-adrenergic receptor system of human lymphocytes. 130 62

The physiologic responses to an intense heat acclimation (HA) regimen (treadmill, 41.2 degrees C, 8 days, 56 min exercise/44 min rest) and the effects on stress and fluid balance hormone responses were examined in 13 unacclimated male volunteers. Venous blood samples were collected before (PRE) and after (POST) exercise (days 1, 4, 8) and analyzed for plasma renin activity (PRA), aldosterone (ALD), cortisol (PC), plasma volume shifts (delta PV%), sodium concentration (Na+), and potassium concentration (K+). HA responses (day 1 vs day 8) indicated reduced strain (P less than 0.05): decreased heart rate, rectal temperature, skin temperature, improved defense of PV, and attenuated PC responses. While plasma Na+ demonstrated no change during daily exercise, K+ (P less than 0.01), PC, PRA, and ALD increased (P less than 0.05) more than delta PV%(day 1: -7.1%, day 8: -5.1%) accounted for. Na+ and K+ did not change as a result of HA, and there was no change in fluid balance hormones (e.g., PRA, ALD). It was concluded that this intense heat acclimation regimen reduced physiologic strain by mechanisms other than alterations in fluid balance hormones and offered few physiologic advantages which cannot be gained through conventional heat acclimation techniques (e.g., walking).
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PMID:Plasma cortisol, renin, and aldosterone during an intense heat acclimation program. 264 46

DNA photolyase catalyzes the photoreversal of pyrimidine dimers. The enzymes from Escherichia coli and yeast contain a flavin chromophore and a folate cofactor, 5,10-methenyltetrahydropteroylpolyglutamate. E. coli DNA photolyase contains about 0.3 mol of folate/mol flavin, whereas the yeast photolyase contains the full complement of folate. E. coli DNA photolyase is reconstituted to a full complement of the folate by addition of 5,10-methenyltetrahydrofolate to cell lysates or purified enzyme samples. The reconstituted enzyme displays a higher photolytic cross section under limiting light. Treatment of photolyase with sodium borohydride or repeated camera flashing results in the disappearance of the absorption band at 384 nm and is correlated with the formation of modified products from the enzyme-bound 5,10-methenyltetrahydrofolate. Photolyase modified in this manner has a decreased photolytic cross section under limiting light. Borohydride reduction results in the formation of 5,10-methylenetetrahydrofolate and 5-methyltetrahydrofolate, both of which are released from the enzyme. Repeated camera flashing results in photodecomposition of the enzyme-bound 5,10-methenyltetrahydrofolate and release of the decomposition products. Finally, it is observed that photolyase binds 10-formyltetrahydrofolate and appears to cyclize it to form the 5,10-methenyltetrahydrofolate chromophore.
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PMID:Role of enzyme-bound 5,10-methenyltetrahydropteroylpolyglutamate in catalysis by Escherichia coli DNA photolyase. 265 1

DNA photolyase from Escherichia coli contains reduced flavin adenine dinucleotide plus a second chromophore, partially characterized in previous studies. Both chromophores function as sensitizers in catalysis. The second chromophore has been identified as a 6-substituted pterin derivative. The compound is oxidized with permanganate to yield 6-carboxypterin or reduced with sodium cyanoborohydride to yield a 5,6,7,8-tetrahydropterin derivative. The second chromophore exhibits spectral properties (lambda max = 360, 255 nm, pH 2) similar to that observed for 7,8-dihydropterin cations. The compound does not exhibit a spectrally detectable pKa around 4 but is converted to a dication (lambda max = 346, 255 nm) in strong acid (pKa approximately 1). Similar ionization behavior is observed with 7,8-dihydropterin derivatives that are alkylated at N(5). The instability of the second chromophore in weakly alkaline solution is due to a fully reversible conversion to a labile bleached form. As compared with other pterin derivatives, the hydrolytic instability is unusual but is very similar to that observed for 5,6-dialkyl-7,8-dihydropterinium salts. It is proposed that the second chromophore is a 7,8-dihydropterin with substituents at positions 5 and 6. The discovery that a pterin derivative functions as a photosensitizer in DNA repair is apparently the first example of a photobiological function for pterins.
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PMID:Identification of a pterin derivative in Escherichia coli DNA photolyase. 304 82

DNA photolyase from Escherichia coli contains FAD plus a partially characterized, second chromophore. In vivo, the flavin is fully reduced (FADH2), but oxidation to a stable, blue radical (FADH.) occurs during enzyme isolation. The second chromophore is irreversibly reduced by reaction of the enzyme with sodium borohydride or by photoreduction in the presence of dithiothreitol. A similar reaction occurs with the protein-free chromophore and sodium cyanoborohydride. Reduction of the second chromophore is accompanied by a complete loss of the chromophore's visible absorption and fluorescence but does not significantly affect catalytic activity. The results show that the enzyme can repair dimers by a pathway involving only FADH2. Enzyme-bound FADH2 is fluorescent and exhibits emission (505 nm) and absorption (360 nm) maxima similar to that expected for a 1,5-dihydroflavin derivative. It is proposed that dimer cleavage via the second chromophore independent pathway involves electron donation from excited FADH2 to pyrimidine dimer. Pyrimidine dimer radicals are unstable and spontaneously monomerize. Unmodified second chromophore can also act as a sensitizer in a pathway that requires FADH2. This pathway may be similar to that proposed for the second chromophore independent reaction except that excited FADH2 would be produced via energy transfer from the excited second chromophore. The fluorescence observed for enzyme-bound, unmodified second chromophore is quenched by FADH. and increases 6-fold when the latter is reduced, but the absorption spectrum (lambda max = 390 nm epsilon 390 = 12.7 x 10(3) M-1 cm-1) is independent of the redox state of the flavin.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:DNA repair catalyzed by Escherichia coli DNA photolyase containing only reduced flavin: elimination of the enzyme's second chromophore by reduction with sodium borohydride. 332 90

DNA photolyase purified from baker's yeast by affinity chromatography on UV-irradiated DNA noncovalently bound to cellulose and by chromatography on activated thiol-Sepharose 4B yields a single protein band having a molecular weight of 51 000 when analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight, 53 000, determined by gel filtration was in good agreement. Upon denaturation of photolyase by heat or 8 M urea, flavin adenine dinucleotide (oxidized) was isolated from the mixture and identified by thin-layer chromatography and spectral analysis. In contrast to flavoproteins to which flavin adenine dinucleotide (oxidized) is bound which generally exhibit two absorbance maxima between 300 and 500 nm, photolyase has only one at 380 nm. These findings and the similar characteristics of the absorbance and emission spectra of native photolyase with those of flavoproteins in which the chromophore is considered to be the 4a,5-reduced flavin have led us to propose this configuration for the photolyase chromophore. The difference in properties of yeast photolyase compared to the one reported previously supports the idea that there are two photolyases in baker's yeast.
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PMID:Evidence that deoxyribonucleic acid photolyase from baker's yeast is a flavoprotein. 698 94

The nontransformed steroid receptors contain several non-steroid binding proteins, such as hsp90, hsp70, and p59. Recently, we and others have shown that p59 (FKBP59) is an immunophilin which binds two potent immunosuppressants, FK506 and rapamycin. This raises the possibility that FK506 or rapamycin may modify the function of steroid receptors. To develop this line of inquiry, we chose a yeast model system in which the human progesterone receptor form B (hPR-B) was cotransformed with a reporter gene. The reporter contains two copies of a progesterone response element/glucocorticoid response element (PRE/GRE) upstream of the CYC1 promoter which are linked to the lacZ gene of Escherichia coli. We found that FK506 potentiated the ability of progesterone in activating transcription. To gain insight into the mechanism of FK506's regulation of PR action, we questioned whether calcineurin is involved, because it has been shown that FK506 is a specific inhibitor of calcineurin, a Ca(2+)- and calmodulin-regulated phosphatase, through the formation of an FKBP12-FK506-calcineurin-calmodulin complex. We found that 15-O-desmethyl-FK520, an FK506 analogue which is an excellent ligand of FKBP12, but a poor inhibitor of calcineurin, failed to induce the same effect as FK506. We also found that calmidazolium, a calmodulin antagonist, mimicked FK506's action. Furthermore, immunoblot analysis showed that both FK506 and calmidazolium potentiated the effect of progesterone in decreasing the mobility of hPR-B upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This suggests that FK506 and calmidazolium may cooperate with progesterone in increasing the level of hPR-B phosphorylation.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Potentiation of progesterone receptor-mediated transcription by the immunosuppressant FK506. 752 Dec 10

The glycosylase/abasic lyase T4 endonuclease V initiates the repair of ultraviolet light-induced pyrimidine dimers. This enzyme forms an imino intermediate between its N-terminal alpha-NH2 group and C-1' of the 5'-residue within the dimer. Sodium borohydride was used to covalently trap endonuclease V to a 49-base pair oligodeoxynucleotide containing a site-specific cyclobutane thymine dimer. The bound and free oligonucleotides were then subjected to nuclease protection assays using DNase I and a complex of 1,10-phenanthroline-copper. There was a large region of protection from both nucleases produced by endonuclease V evident on the strand opposite and asymmetrically opposed to the dimer. Little protection was seen on the dimer-containing strand. The existence of a footprint with the 1,10-phenanthroline-copper cleavage agent indicated that endonuclease V was interacting with the DNA predominantly via the minor groove. Methylation by dimethyl sulfate yielded no areas of protection when endonuclease V was covalently attached to the DNA, indicating that the protein may closely approach the DNA without direct contact with the bases near the thymine dimer. The Escherichia coli proteins Fpg and photolyase display a very different pattern of nuclease protection on their respective substrates, implying that endonuclease V recognizes pyrimidine dimers by a novel mechanism.
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PMID:T4 endonuclease V protects the DNA strand opposite a thymine dimer from cleavage by the footprinting reagents DNase I and 1,10-phenanthroline-copper. 787 17

The (6-4)photoproduct DNA photolyase ((6-4)photolyase) repairs UV-induced pyrimidine (6-4) pyrimidone photoproduct ((6-4)photoproduct, pyr[6,4]pyr) in a light dependent manner. Drosophila (6-4)photolyase was purified to near homogeneity from Drosophila embryonic cells and is shown to be a 62 kDa protein as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified (6-4)photolyase repairs (6-4)photoproducts induced at 5'-CC-3' site (C[6,4]C) as well as T[6,4]T and T[6,4]C. Photoreactivation of (6-4)photoproduct constructed in M13 phage eliminates the replication block and abolishes induced mutagenesis in E. coli cells, suggesting that the (6-4)photolyase repairs the photoproduct to the unmodified form.
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PMID:Non-mutagenic repair of (6-4)photoproducts by (6-4)photolyase purified from Drosophila melanogaster. 944 30


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