Phot-LOV1: photocycle of a blue-light receptor domain from the green alga Chlamydomonas reinhardtii.
The "Phot" protein family comprises blue-light photoreceptors that consist of two flavin mononucleotide (FMN)-binding LOV (light, oxygen, and voltage) domains and a serine/threonine kinase domain. We have investigated the LOV1 domain of Phot1 from Chlamydomonas reinhardtii by time-resolved absorption spectroscopy. Photoexcitation of the dark form, LOV1-447, causes transient bleaching and formation of two spectrally similar red-shifted intermediates that are both assigned to triplet states of the FMN. The triplet states decay with time constants of 800 ns and 4 micro s with an efficiency of >90% into a blue-shifted intermediate, LOV1-390, that is attributed to a thiol adduct of cysteine 57 to FMN C(4a). LOV1-390 reverts to the dark form in hundreds of seconds, the time constant being dependent on pH and salt concentration. In the mutant C57S, where the thiol adduct cannot be formed, the triplet state displays an oxygen-dependent decay directly to the dark form. We present here a spectroscopic characterization of an algal sensory photoreceptor in general and of a LOV1 domain photocycle in particular. The results are discussed with respect to the behavior of the homologous LOV2 domain from oat.
Kottke
Tilman
T
Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93053 Regensburg, Germany. tilman.kottke@uni-regensburg.de
Heberle
Joachim
J
Hehn
Dominic
D
Dick
Bernhard
B
Hegemann
Peter
P
D000818:Animals; D001426:Bacterial Proteins; D016825:Chlamydomonas reinhardtii / Q000737:chemistry; D056931:Cryptochromes; D003624:Darkness; D029721:Drosophila Proteins; D005136:Eye Proteins; D005486:Flavin Mononucleotide / Q000737:chemistry* / Q000528:radiation effects*; D005420:Flavoproteins / Q000737:chemistry* / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D008027:Light; D008958:Models, Molecular; D010777:Photochemistry / Q000379:methods; D017956:Photoreceptor Cells, Invertebrate / Q000737:chemistry; D017434:Protein Structure, Tertiary; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods
D001426:Bacterial Proteins; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D043562:Receptors, G-Protein-Coupled; D011993:Recombinant Fusion Proteins; C102287:RulA protein, Pseudomonas syringae; C119828:cry protein, Drosophila; D012965:Sodium Chloride; D005486:Flavin Mononucleotide