Sub-nanosecond tryptophan radical deprotonation mediated by a protein-bound water cluster in class II DNA photolyases

Abstract

Light activation of class II DNA photolyases is enhanced by a unique cluster of protein-bound water molecules.

Delocalized hole transport coupled to sub-ns tryptophanyl deprotonation promotes photoreduction of class II photolyases

“…(and ignoring possible excited-state deactivation through electron transfer from the adenine moiety of FAD during step 1, as previously reported 22 ), the total quantum yield of charge separation at the end of step 3 can be estimated to 43%, which is rather close to the value of ~55% derived differently by Müller et al 33 Interestingly, a specific region of EADS4, around 400 nm, is not well reproduced by this spectral fit ( Figure 4C)…”

“…7,33 Our anisotropy measurements confirm the assignment of W 381 H •+ as the primary oxidized species formed within the 9.2 ps phase. Furthermore, it appears that not all of the excited flavins are reduced during the initial phase and that a small fraction of them only decays during the second kinetic phase, in 29 ps.…”

“…The Methanosarcina mazei class II photolyase (MmCPDII) was prepared as previously described. 7,13,33 For the transient absorption experiments, we used a 10 mM…”

“…12,13 Figure 1 illustrates this triad (W 381 , W 360 and W 388 ) for the class II photolyase of Methanosarcina mazei (noted MmCPDII), according to the crystal structure of Kiontke et al 13 (PDB entry 2XRY). Recently, Müller et al 33 have shown by ns-ms transient absorption spectroscopy that the distal W 388 H…”

“…Accordingly, it was proposed that Y 345 gets partially oxidized in the sub-ms regime, in competition with recombination of the FAD We report here the first ultrafast spectroscopic study of the photoactivation of a class II photolyase, namely MmCPDII. The major objective is to explore the dynamics of this reaction in the fs-ps timescale that escaped Müller et al's study, 33 and compare it to other known photolyases and cryptochromes. The present study has been conducted on both the wild-type (WT) of MmCPDII and its Y345F mutant (shortcuts WT and Y345F will be subsequently used to designate them.…”