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Byrdin, M ; Villette, S ; Eker, APM ; Brettel, K

Observation of an intermediate tryptophanyl radical in W306F mutant DNA photolyase from Escherichia coli supports electron hopping along the triple tryptophan chain

Biochemistry 46 (35) 10072-10077

par Administrateur - publié le

Abstract :

DNA photolyases repair UV-induced cyclobutane pyrimidine dimers in DNA by photoinduced electron transfer. The redox-active cofactor is FAD in its doubly reduced state FADH(-). Typically, during enzyme purification, the flavin is oxidized to its singly reduced semiquinone state FADH degrees. The catalytically potent state FADH(-) can be reestablished by so-called photoactivation. Upon photoexcitation, the FADH degrees is reduced by an intrinsic amino acid, the tryptophan W306 in Escherichia coli photolyase, which is 15 A distant. Initially, it has been believed that the electron passes directly from W306 to excited FADH degrees, in line with a report that replacement of W306 with redox-inactive phenylalanine (W306F mutant) suppressed the electron transfer to the flavin [Li, Y. F., et al. (1991) Biochemistry 30, 6322-6329].