Electron Paramagnetic Resonance Spectroscopy on Flavin Cofactors in Blue-Light Receptors

• Applicant: Professor Dr. Robert Bittl
• Subject Area: Biophysics
• Term: from 2004 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5470629

Flavin chromophores occur in blue-light dependent enzymes and photoreceptors: Flavin adenine dinucleotide (FAD) is found in the photolyase DNA-repair enzymes and the related cryptochromes, UV-A/blue-light photoreceptors, and photoreceptors of the BLUF domain type, whereas flavin mononucleotide (FMN) is present as non-covalently bound cofactor in the LOV-domain type photoreceptors. The function of the flavin chromophore is not yet understood in all the different proteins. In some proteins, flavin paramagnetic states, radical or triplet states, play an essential role. These states are accessible to electron paramagnetic resonance (EPR) techniques. With EPR methods, questions regarding the specific binding situation of the chromophore as well as the molecular mechanism of the protein function as a result of the interaction between protein and cofactor can be addressed. In the framework of the Research Group "Blue-light Sensitive Biological Photoreceptors" we will analyze the binding situation of the FAD cofactor in the BLUF domain proteins AppA and PCA/B which are involved in light-regulated protein synthesis and cyclase activity, respectively, and in animal and plant cryptochromes. This will be done by analysis of the zero-field splitting parameters of the FAD triplet states and the hyperfine and Zeeman-interaction parameters of FAD radicals. In several cryptochromes, electron-transfer activity involving amino acids has been postulated. With time-resolved EPR techniques we will identify the amino-acid species involved in the electron-transfer chain of these systems.

• DFG Programme: Research Units
• Subproject of: FOR 526: Blue-light Sensitive Photoreceptors
• Major Instrumentation: Nd: YAG-Laser und OPO-Laser
• Instrumentation Group: 5700 Festkörper-Laser
• Participating Person: Professor Dr. Stefan Weber