A Second Conserved GAF Domain Cysteine Is Required for the Blue/Green Photoreversibility of Cyanobacteriochrome Tlr0924 from Thermosynechococcus elongatus
- 13 June 2008
- journal article
- research article
- Published by American Chemical Society (ACS) in Biochemistry
- Vol. 47 (27), 7304-7316
- https://doi.org/10.1021/bi800088t
Abstract
Phytochromes are widely occurring red/far-red photoreceptors that utilize a linear tetrapyrrole (bilin) chromophore covalently bound within a knotted PAS-GAF domain pair. Cyanobacteria also contain more distant relatives of phytochromes that lack this knot, such as the phytochrome-related cyanobacteriochromes implicated to function as blue/green switchable photoreceptors. In this study, we characterize the cyanobacteriochrome Tlr0924 from the thermophilic cyanobacterium Thermosynechococcus elongatus. Full-length Tlr0924 exhibits blue/green photoconversion across a broad range of temperatures, including physiologically relevant temperatures for this organism. Spectroscopic characterization of Tlr0924 demonstrates that its green-absorbing state is in equilibrium with a labile, spectrally distinct blue-absorbing species. The photochemically generated blue-absorbing state is in equilibrium with another species absorbing at longer wavelengths, giving a total of 4 states. Cys499 is essential for this behavior, because mutagenesis of this residue results in red-absorbing mutant biliproteins. Characterization of the C499D mutant protein by absorbance and CD spectroscopy supports the conclusion that its bilin chromophore adopts a similar conformation to the red-light-absorbing Pr form of phytochrome. We propose a model photocycle in which Z/E photoisomerization of the 15/16 bond modulates formation of a reversible thioether linkage between Cys499 and C10 of the chromophore, providing the basis for the blue/green switching of cyanobacteriochromes.Keywords
This publication has 75 references indexed in Scilit:
- Mutational Analysis of Deinococcus radiodurans Bacteriophytochrome Reveals Key Amino Acids Necessary for the Photochromicity and Proton Exchange Cycle of PhytochromesPublished by Elsevier BV ,2008
- Crystal structure of the chromophore binding domain of an unusual bacteriophytochrome, RpBphP3, reveals residues that modulate photoconversionProceedings of the National Academy of Sciences of the United States of America, 2007
- Characterization of Cyanobacteriochrome TePixJ from a Thermophilic Cyanobacterium Thermosynechococcus elongatus Strain BP-1Plant and Cell Physiology, 2006
- PHYTOCHROME STRUCTURE AND SIGNALING MECHANISMSAnnual Review of Plant Biology, 2006
- MUSCLE: multiple sequence alignment with high accuracy and high throughputNucleic Acids Research, 2004
- RcaE is a complementary chromatic adaptation photoreceptor required for green and red light responsivenessMolecular Microbiology, 2004
- Modeller: Generation and Refinement of Homology-Based Protein Structure ModelsMethods in Enzymology, 2003
- VMD: Visual molecular dynamicsJournal of Molecular Graphics, 1996
- Refined three-dimensional structure of phycoerythrocyanin from the cyanobacterium Mastigocladus laminosus at 2.7 ÅJournal of Molecular Biology, 1990
- UV-visible absorption and circular dichroism spectra of the subunits of C-phycocyanin I: Quantitative assessment of the effect of chromophore—protein interaction in the α-subunitJournal of Photochemistry and Photobiology B: Biology, 1989