Photoreceptors, blue-light

Using blue-light photoreceptors from Bacillus subtilis and Pseudomonas putida that contain light-oxygen-voltage sensing domains, flavin mononucleotide-based fluorescent proteins were produced that can be used as fluorescent reporters in both aerobic and anaerobic biological systems. 

Thresher RJ, Vitatema MH, Miyamoto Y et al 1998 Role of mouse cryptochrome blue-light photoreceptor in circadian photoresponses. Science 282 1490-1494... 

Egan ES, Franklin TM, Hilderbrand-Chae MJ et al 1999 An extraretinally expressed insect cryptochrome with similarity to the blue light photoreceptors of mammals and plants. J Neurosci 19 3665-3673... 

From such a viewpoint, we are examining primary processes of photoreactions of PYP [1] which functions as a blue light photoreceptor for a negative phototaxis of the purple sulfur bacterium Ectothiorhodospira halophila, some FP s [2] and Rh [3] by means of the fs fluorescence up-conversion measurements. In this article, we will discuss our latest results of fs fluorescence dynamics studies on PYP, because PYP is very stable for repeated irradiation which induces photocycles so that the very accurate experimental results can be obtained rather easily and also the preparation of the site-directed mutants as well as the PYP analogues with modified chromophores are rather easy. However, before that, we will summarize briefly results of our previous investigations. 

The Photoactive Yellow Protein (PYP) is the blue-light photoreceptor that presumably mediates negative phototaxis of the purple bacterium Halorhodospira halophila [1]. Its chromophore is the deprotonated trans-p-coumaric acid covalently linked, via a thioester bond, to the unique cystein residue of the protein. Like for rhodopsins, the trans to cis isomerization of the chromophore was shown to be the first overall step of the PYP photocycle, but the reaction path that leads to the formation of the cis isomer is not clear yet (for review see [2]). From time-resolved spectroscopy measurements on native PYP in solution, it came out that the excited-state deactivation involves a series of fast events on the subpicosecond and picosecond timescales correlated to the chromophore reconfiguration [3-7]. On the other hand, chromophore H-bonding to the nearest amino acids was shown to play a key role in the trans excited state decay kinetics [3,8]. In an attempt to evaluate further the role of the mesoscopic environment in the photophysics of PYP, we made a comparative study of the native and denatured PYP. The excited-state relaxation path and kinetics were monitored by subpicosecond time-resolved absorption and gain spectroscopy. 

Figure 23.2. Reaction mechanism of PD-DNA photolyase. A photon of blue light is absorbed by the MTHF chromophore that acts as a photoantenna. The excited energy is transferred to the flavin chromophore (FADFF). The excited flavin (FADFI ) acts as a photocatalyst and transfers an electron to a CPD in DNA. The thymines are restored to their native state and the electron is transferred back to the flavin. (Reproduced with permission from Sancar, A. Structure and function of DNA photolyase cryptochrome blue-light photoreceptors. Chem. Rev. 103, 2203-2237, 2003.)...

Sancar, A. Structure and function of DNA photolyase cryptochrome blue-light photoreceptors. Chem Rev. 103, 2203-2237, 2003. 

Fig. 3. Examples of natural photoantenna chromophores (2) 5,10-methenyltetrahydrofolate (MTHF), a blue light photoreceptor pigment present in photolyase and some cryptochromes (3) Pheophytin a, the primary electron acceptor in cyanobacterial oxygenic photosynthesis. (4) 11-cis-retinal, which is involved as sensory photoreceptor component in the opsin-based visual process of animals and (5) the p-hydroxy-benzylidene-imidazolinone chromophore (HBDI) of the green fluorescent protein from bioluminescent marine species.

Structure and function of DNA photolyase and cryptochrome blue-light photoreceptors 03CRV2203. 

Redox reactions have been proposed to play a key role in light-responsive activities of cryptochromes [98, 99], blue-light photoreceptors in plants, animals, and bacteria with widespread functions ranging from the regulation of circadian rhythms of plants and animals [13] to the sensing of magnetic fields in a number of species... 

Cryptochrome/photolyase blue light photoreceptor family. The photoreceptors in this family are flavoproteins. They have a wide range of functions including circadian clock regulation, seed germination, and pigment accumulation. 

Miyazawa, Y., H. Nishioka, et al. (2008). Discrimination of class I cyclobutane pyrimidine dimer photolyase from blue light photoreceptors by single methionine residue. Biophysics Journal 94(6) 2194-2203. 

---