In @entity526 photolyase, excitation of the FAD cofactor in its semireduced radical state (FADH*) induces an electron transfer over approximately 15 A from @entity2340 W306 to the @entity1785 . It has been suggested that two additional tryptophans are involved in an electron transfer chain FADH* <-- W382 <-- W359 <-- W306. To test this hypothesis, we have mutated W382 into redox inert @entity815 . Ultrafast transient absorption studies showed that, in @entity7097 photolyase, excited FADH* decayed with a time constant tau approximately 26 ps to fully reduced @entity1785 and a @entity2340 cation radical. In @entity70270 mutant photolyase, the excited @entity1785 was much longer lived (tau approximately 80 ps), and no significant amount of product was detected. We conclude that, in @entity7097 photolyase, excited FADH* is quenched by electron transfer from W382. On a millisecond scale, a product state with extremely low yield ( approximately 0.5% of @entity7097 ) was detected in @entity70270 mutant photolyase. Its spectral and kinetic features were similar to the fully reduced @entity1785 /neutral @entity2340 radical state in @entity7097 photolyase. We suggest that, in @entity70270 mutant photolyase, excited FADH* is reduced by W359 at a rate that competes only poorly with the intrinsic decay of excited FADH* (tau approximately 80 ps), explaining the low product yield. Subsequently, the W359 cation radical is reduced by W306. The rate constants of electron transfer from W382 to excited FADH* in @entity7097 and from W359 to excited FADH* in @entity70270 mutant photolyase were estimated and related to the donor-acceptor distances.

Dissection of the triple @entity2340 electron transfer chain in XXXX DNA photolyase: Trp382 is the primary donor in photoactivation.

@entity1785 :: ('MESH:C024132', 'Chemical') :: ['flavin'] @entity7097 :: ('MESH:C536751', 'Disease') :: ['WT'] @entity2340 :: ('CHEBI:27897', 'Chemical') :: ['tryptophan'] @entity70270 :: ('p|SUB|W|382|F', 'ProteinMutation') :: ['W382F'] @entity815 :: ('CHEBI:28044', 'Chemical') :: ['phenylalanine'] @entity526 :: ('562', 'Species') :: ['Escherichia coli']
@entity526 :: (562,Species) :: ['Escherichia coli']
