Photoreactivation in a phrB mutant of Escherichia coli K-12: evidence for the role of a second protein in photorepair.
In Escherichia coli, the light-dependent repair of pyrimidine dimers in UV-irradiated DNA is now accepted as being due to enzymatic photoreactivation (PR) by a 50 kDa enzyme, photolyase (EC 4.1.99.3). The gene for this enzyme has been mapped at 16.2 min and designated phr. This gene was earlier described as phrB, another locus phrA having been proposed in association with PR. The relevance of the putative phrA gene has now been placed in doubt. The recent report of the discovery of a photoreactivating enzyme in Drosophila melanogaster, which specifically repairs pyrimidine (6-4) pyrimidone photoproducts ([6-4] photoproducts), and that E. coli does possess a protein with specific affinity for the (6-4) photoproduct, has cast new light on the prospective role of phrA in PR. We have determined the nucleotide sequence of the putative phrA gene, which suggests it codes for a protein of 38 kDa. When the putative phrA gene was cloned into an expression vector and transformed into a phrA phrB mutant of E. coli, a level of photorepair was observed, which could correspond to repair of (6-4) photoproducts.
Dorrell
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N
School of Pharmacy and Pharmacology, University of Bath, Avon, UK.
Ahmed
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AH
Moss
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SH
D018528:ATP-Binding Cassette Transporters; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D003062:Codon; D004260:DNA Repair / Q000235:genetics*; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000528:radiation effects*; D029968:Escherichia coli Proteins; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D014176:Protein Biosynthesis; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D017422:Sequence Analysis, DNA; D014158:Transcription, Genetic; D014466:Ultraviolet Rays
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; D003062:Codon; D029968:Escherichia coli Proteins; C085800:modF protein, E coli; D004255:Deoxyribodipyrimidine Photo-Lyase