title: Analysis of the role of intraprotein electron transfer in photoreactivation by DNA photolyase in vivo.
abstract: Escherichia coli DNA photolyase contains FADH(-) as the catalytic cofactor. The cofactor becomes oxidized to the FADH(*) blue neutral radical during purification. The E-FADH(*) form of the enzyme is catalytically inert but can be converted to the active E-FADH(-) form by a photoreduction reaction that involves intraprotein electron transfer from Trp306. It is thought that the E-FADH(*) form is also transiently generated during pyrimidine dimer repair by photoinduced electron transfer, and it has been suggested that the FADH(*) that is generated after each round of catalysis must be photoreduced before the enzyme can engage in subsequent rounds of repair. In this study, we introduced the Trp306Phe mutation into the chromosomal gene and tested the non-photoreducible W306F mutant for photorepair in vivo. We find that both wild-type and W306F mutant photolyases carry out at least 25 rounds of photorepair at the same rate. We conclude that photoreduction by intraprotein electron transfer is not part of the photolyase photocycle under physiological conditions.
authors.affiliation: Department of Biochemistry and Biophysics, University of North Carolina School of Medicine, Chapel Hill, North Carolina 27599, USA.
authors.forename: I Halil
authors.initials: IH
authors.lastname: Kavakli
authors.forename: Aziz
authors.initials: A
authors.lastname: Sancar
mesh_terms: D002384:Catalysis; D004260:DNA Repair / Q000235:genetics; D004255:Deoxyribodipyrimidine Photo-Lyase / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D004579:Electron Transport / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D005182:Flavin-Adenine Dinucleotide / Q000031:analogs & derivatives* / Q000378:metabolism; D010649:Phenylalanine / Q000235:genetics; D010777:Photochemistry; D011740:Pyrimidine Dimers / Q000737:chemistry; D014364:Tryptophan / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D011740:Pyrimidine Dimers; D005182:Flavin-Adenine Dinucleotide; C058805:1,5-dihydro-FAD; D010649:Phenylalanine; D014364:Tryptophan; D004255:Deoxyribodipyrimidine Photo-Lyase