Journal
BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS
Volume 1655, Issue 1-3, Pages 64-70Publisher
ELSEVIER
DOI: 10.1016/j.bbabio.2003.07.001
Keywords
photolyase; electron transfer; proton transfer; tryptophan radical; deuterium isotope effect; transient absorption spectroscopy
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We review our work on electron transfer and proton dynamics during photoactivation in DNA photolyase from E. coli and discuss a recent theoretical study on this issue. In addition, we present unpublished data on the charge recombination between the fully reduced FADH(-) and the neutral (deprotonated) radical of the solvent exposed tryptophan W306. We found a pronounced acceleration with decreasing pH and an inverse deuterium isotope effect (k(H)/k(D)) = 0.35 at pL 6.5) and interpret it in a model of a fast protonation equilibrium for the W306 radical. Due to this fast equilibrium, two parallel recombination channels contribute differently at different pH values: one where reprotonation of the W306 radical is followed by electron transfer from FADH(-) (electron transfer time constant tau(et) in the order of 10-50 mus), and one where electron transfer from FADH(-) (tau(et) = 25 ms) is followed by reprotonation of the W306 anion. (C) 2004 Elsevier B.V. All rights reserved.
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