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)

A purification procedure consisting of Biorex-70, single-stranded DNA-agarose, and ultraviolet (UV) light irradiated DNA-cellulose chromatography has been adopted for the Escherichia coli photoreactivating enzyme. The purpose of this purification was to obtain enzyme preparations that are free of extraneous nucleic acid or nucleotides. The purification yields high specific activities (75 000 pmol h-1 mg-1) with a 50% recovery. Enzyme preparations have also been obtained from UV-irradiated DNA-cellulose by exposure to visible light. These enzyme preparations contain oligoribonucleotides, the largest found to be 26 nucleotides in length in relation to DNA size markers. However, the oligoribonucleotides associated with the enzyme are not essential for enzymatic activity. When the enzyme is preincubated with exogenous ATP for 4-10 h at 3 degrees C, a 10-fold stimulation in the enzyme activity has been observed. It has been determined by polyacrylamide gel electrophoresis and high-voltage diethylaminoethyl paper electrophoresis that the light-released enzyme samples from a preincubated and washed mixture of the enzyme, [gamma-32P]ATP, and UV-irradiated DNA-cellulose contained exogenous [gamma-32P]ATP. [gamma-32P]ATP eluted with the enzyme-containing fractions when subjected to Bio-Gel P-30 chromatography. GTP caused a slight enhancement of the enzyme activity while ADP strongly inhibited photoreactivation, at the same concentration and conditions as those for ATP. Higher (X5) concentrations of ADP and adenosine 5'-(beta, gamma-methylenetriphosphate) totally inhibited the enzyme activity. Dialysis of a photoreactivating enzyme preparation against a buffer solution containing 1 mM ATP caused a 9-fold stimulation of the enzyme activity.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Stimulation of Escherichia coli DNA photoreactivating enzyme activity by adenosine 5'-triphosphate. 638 May 77

Exposure to solar radiation can cause mortality in natural communities of pico-phytoplankton, both at the surface and to a depth of at least 30 m. DNA damage is a significant cause of death, mainly due to cyclobutane pyrimidine dimer formation, which can be lethal if not repaired. While developing a UV mutagenesis protocol for the marine cyanobacterium Prochlorococcus, we isolated a UV-hyper-resistant variant of high light-adapted strain MED4. The hyper-resistant strain was constitutively upregulated for expression of the mutT-phrB operon, encoding nudix hydrolase and photolyase, both of which are involved in repair of DNA damage that can be caused by UV light. Photolyase (PhrB) breaks pyrimidine dimers typically caused by UV exposure, using energy from visible light in the process known as photoreactivation. Nudix hydrolase (MutT) hydrolyses 8-oxo-dGTP, an aberrant form of GTP that results from oxidizing conditions, including UV radiation, thus impeding mispairing and mutagenesis by preventing incorporation of the aberrant form into DNA. These processes are error-free, in contrast to error-prone SOS dark repair systems that are widespread in bacteria. The UV-hyper-resistant strain contained only a single mutation: a 1 bp deletion in the intergenic region directly upstream of the mutT-phrB operon. Two subsequent enrichments for MED4 UV-hyper-resistant strains from MED4 wild-type cultures gave rise to strains containing this same 1 bp deletion, affirming its connection to the hyper-resistant phenotype. These results have implications for Prochlorococcus DNA repair mechanisms, genome stability and possibly lysogeny.
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PMID:UV hyper-resistance in Prochlorococcus MED4 results from a single base pair deletion just upstream of an operon encoding nudix hydrolase and photolyase. 2034 42