Ultrafast photoreduction dynamics of a new class of CPD photolyases

Abstract

NewPHL is a recently discovered subgroup of ancestral DNA photolyases. Its domain architecture displays pronounced differences from that of canonical photolyases, in particular at the level of the characteristic electron transfer chain, which is limited to merely two tryptophans, instead of the "classical" three or four. Using transient absorption spectroscopy, we show that the dynamics of photoreduction of the oxidized FAD cofactor in the NewPHL begins similarly as that in canonical photolyases, i.e., with a sub-ps primary reduction of the excited FAD cofactor by an adjacent tryptophan, followed by migration of the electron hole towards the second tryptophan in the tens of ps regime. However, the resulting tryptophanyl radical then undergoes an unprecedentedly fast deprotonation in less than 100 ps in the NewPHL. In spite of the stabilization effect of this deprotonation, almost complete charge recombination follows in two phases of ~ 950 ps and ~ 50 ns. Such a rapid recombination of the radical pair implies that the first FAD photoreduction step, i.e., conversion of the fully oxidized to the semi-quinone state, should be rather difficult in vivo. We hence suggest that the flavin chromophore likely switches only between its semi-reduced and fully reduced form in NewPHL under physiological conditions.

Limited solvation of an electron donating tryptophan stabilizes a photoinduced charge-separated state in plant (6–4) photolyase

“…For comparison, in E. coli CPD PL ~ 35% of the photoinduced radical pairs are lost within the first few ns 38 , in Chlamydomonas reinhardtii animal-like CRY it is ~ 50% 25 , in Xl 64 ~ 75% 21 , and in At CRY 80 to 95%, depending on the presence or absence of ATP 17 . In Dinoroseobacter shibae NewPHL, which is an ancestral PL containing a mere Trp dyad, as much as ~ 90% of the photoinduced radical pairs are lost within the first few nanoseconds and most of the remaining ~ 10% pairs recombine within the next ~ 50 ns 39 . Interestingly, our structural comparison between At 64 and Xl 64 does not show any remarkable difference in the residues within 4 Å of FAD and Trp 1 H (Supplementary Fig.…”

Photosensory and Signaling Properties of Cryptochromes

“…Большинство данных по фотохимии криптохромов получено при изучении CRY1/CRY2 A. thaliana, CPH1 и CraCRY C. reinhardtii и dCRY D. melanogaster [14,[19][20][21][22]. В отличие от фотолиаз, эти криптохромы в основном состоянии содержат ФАД в полностью окисленной форме и обычно (за исключением CraCRY, который дополнительно встраивает хромофор 8-HDF) не связывают антенный хромофор.…”