title: First evidence for phototropin-related blue-light receptors in prokaryotes.
abstract: A prokaryotic protein, YtvA from Bacillus subtilis, was found to possess a light, oxygen, voltage (LOV) domain sharing high homology with the photoactive, flavin mononucleotide (FMN)-binding LOV domains of phototropins (phot), blue-light photoreceptors for phototropism in higher plants. Computer-based three-dimensional modeling suggests that YtvA-LOV binds FMN in a similar pocket as phot-LOVs. Recombinant YtvA indeed exhibits the same spectroscopical features and blue-light-induced photochemistry as phot-LOVs, with the reversible formation of a blue-shifted photoproduct, assigned to an FMN-cysteine thiol adduct (Thio383). By means of laser-flash photolysis and time-resolved optoacoustic experiments, we measured the quantum yield of formation for Thio383, Phi(Thio) = 0.49, and the enthalpy change, DeltaH(Thio) = 135 kJ/mol, with respect to the parent state. The formation of Thio383 is accompanied by a considerable volume contraction, DeltaV(Thio) = -13.5 ml/mol. Similar to phot-LOVs, Thio383 is formed from the decay of a red-shifted transient species, T650, within 2 micros. In both YtvA and free FMN, this transient has an enthalpy content of approximately 200 kJ/mol, and its formation is accompanied by a small contraction, DeltaV(T) approximately -1.5 ml/mol, supporting the assignment of T650 to the FMN triplet state, as suggested by spectroscopical evidences. These are the first studies indicating that phototropin-related, blue-light receptors may exist also in prokaryotes, besides constituting a steadily growing family in plants.
authors.affiliation: Istituto Nazionale per la Fisica della Materia and Department of Physics University of Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy. aba@mpi-muelheim.mpg.de
authors.forename: Aba
authors.initials: A
authors.lastname: Losi
authors.forename: Eugenia
authors.initials: E
authors.lastname: Polverini
authors.forename: Benjamin
authors.initials: B
authors.lastname: Quest
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gärtner
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000378:metabolism* / Q000528:radiation effects; D029681:Arabidopsis Proteins; D001412:Bacillus subtilis / Q000378:metabolism* / Q000528:radiation effects; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001683:Biological Clocks; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D008027:Light; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010777:Photochemistry; D010782:Photolysis; D017956:Photoreceptor Cells, Invertebrate; D011487:Protein Conformation; D011789:Quantum Theory; D043562:Receptors, G-Protein-Coupled; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013816:Thermodynamics
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; C538962:CRY1 protein, Arabidopsis; D056931:Cryptochromes; D029721:Drosophila Proteins; D005136:Eye Proteins; D005420:Flavoproteins; D043562:Receptors, G-Protein-Coupled; C119828:cry protein, Drosophila