Donor−Acceptor Distance-Dependence of Photoinduced Electron-Transfer Rate in Flavoproteins

Tanaka, Fumio; Chosrowjan, Haik; Taniguchi, Seiji; Mataga, Noboru; Sato, Kyosuke; Nishina, Yasuzo; Shiga, Kiyoshi

doi:10.1021/jp066450g

Cited by 58 publications

(73 citation statements)

References 41 publications

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“…Based on the similar architecture of the chicken RfBP and the dodecin binding pockets, we suggest also that in the dodecins HsDod A and HhDod B the indole moieties of the adjacent tryptophans transfer the electron for RF quenching. Considering the tryptophan-isoalloxazine distances of 3.3 Å in the HsDod A and the HhDod B binding pockets, which are shorter than the respective distances of tryptophan (Trp 156 )-isoalloxazine (3.7 Å) and tyrosine (Tyr 75 )-isoalloxazine (3.7 Å) in the chicken RfBP, electron transfer can be estimated to take place within the sub-picosecond time scale (26,27).…”

Section: Time-resolved Spectroscopy Performed On the Dodecins Rf/hsdodmentioning

confidence: 99%

Dodecin Is the Key Player in Flavin Homeostasis of Archaea

Grininger

Staudt

Johansson

et al. 2009

Journal of Biological Chemistry

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Flavins are employed to transform physical input into biological output signals. In this function, flavins catalyze a variety of light-induced reactions and redox processes. However, nature also provides flavoproteins with the ability to uncouple the mediation of signals. Such proteins are the riboflavin-binding proteins (RfBPs) with their function to store riboflavin for fast delivery of FMN and FAD. Here we present in vitro and in vivo data showing that the recently discovered archaeal dodecin is an RfBP, and we reveal that riboflavin storage is not restricted to eukaryotes. However, the function of the prokaryotic RfBP dodecin seems to be adapted to the requirement of a monocellular organism. While in eukaryotes RfBPs are involved in trafficking riboflavin, and dodecin is responsible for the flavin homeostasis of the cell. Although only 68 amino acids in length, dodecin is of high functional versatility in neutralizing riboflavin to protect the cellular environment from uncontrolled flavin reactivity. Besides the predominant ultrafast quenching of excited states, dodecin prevents light-induced riboflavin reactivity by the selective degradation of riboflavin to lumichrome. Coordinated with the high affinity for lumichrome, the directed degradation reaction is neutral to the cellular environment and provides an alternative pathway for suppressing uncontrolled riboflavin reactivity. Intriguingly, the different structural and functional properties of a homologous bacterial dodecin suggest that dodecin has different roles in different kingdoms of life.Flavins are a major class of cofactors that are able to accept and donate electrons as well as to absorb visible light. Flavins consist of a nonconserved aliphatic moiety, covalently linked to a conserved aromatic isoalloxazine ring ( In all flavins, the catalytically active unit is the isoalloxazine substructure (2-4). To handle the reactivity of the isoalloxazine ring, FMN and FAD are tightly bound to flavoenzymes. Finely tuned binding restricts the reaction spectrum of FMN and FAD to discrete, beneficial reaction pathways, preventing harmful side reactions. Reported functions of flavoenzymes include transferring electrons from and to reactive centers (e.g. respiratory chain) as well as employing light for the induction of radical reactions (e.g. DNA-photolyase) or conformational changes (e.g. phototropin) (5-8). In the biosynthesis, the full catalytic power of flavins has already formed at the stage of the FMN and FAD precursor RF (see Fig. 1). As RF is not used as an enzymatically active compound, it is, different to FMN and FAD, not integrated into flavoenzymes. To avoid a negative impact of uncontrolled flavin reactivity by free RF, nature established sequestering devices termed riboflavin-binding proteins (RfBPs). These proteins have been shown to store and distribute RF in eukaryotes, ensuring a fast supply of FMN and FAD (9, 10).The small flavoprotein dodecin from the archaeon Halobacterium salinarum was reported to bind RF with high affinity and to extensiv...

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Section: Time-resolved Spectroscopy Performed On the Dodecins Rf/hsdodmentioning

confidence: 99%

Dodecin Is the Key Player in Flavin Homeostasis of Archaea

Grininger

Staudt

Johansson

et al. 2009

Journal of Biological Chemistry

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show abstract

“…It was found by means of picosecond [19,20] and femtosecond-resolved [21] transient absorption spectroscopy that ET processes from Trp or Tyr to the excited Iso in flavoproteins were responsible for the quenching. Fluorescence decays of several flavoproteins, which were believed to be non-fluorescent, were observed in the time domain of femtoseconds/picoseconds by a fluorescence up-conversion technique [22][23][24][25][26][27]. An empirical equation for ET rate was derived as a function of average distance, R, rather than edge to edge distance, between Iso and nearby Trp or Tyr in flavoproteins [25].…”

Section: Introductionmentioning

confidence: 99%

Analyses of donor–acceptor distance-dependent rates of photo-induced electron transfer in flavoproteins with three kinds of electron transfer theories

et al. 2008

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“…In other words, the donor-acceptor interaction is very strong in CT state, and then the ion pair cannot form. The ''bell shape" of ET rate in the R-representation was also suggested in the flavoprotein systems [14].…”

Section: Discussionmentioning

confidence: 76%

“…In the previous work [13,14] we found that the average distance between both chromophores, rather than edge-to-edge distance, plays an important role for ET.…”

Section: Discussionmentioning

confidence: 82%