TY - JOUR
T1 - A photo-labile thioether linkage to phycoviolobilin provides the foundation for the blue/green photocycles in DXCF-cyanobacteriochromes
AU - Burgie, E. Sethe
AU - Walker, Joseph M.
AU - Phillips, George N.
AU - Vierstra, Richard D.
N1 - Funding Information:
We thank Dr. Andy Ulijasz for the TePixJ(GAF) construction and advice on expression and assembly, Dr. Craig Bingman for aid with crystallomics resources, and Dr. J. Clark Lagarias for the pPL-PCB vector and for helpful discussions. Use of the Advanced Photon Source was supported by the U.S. Department of Energy (DE-AC02-06CH11357), and use of the LS-CAT Sector 21 was supported by a grant from the Michigan Economic Development Corporation and the Michigan Technology Tri-Corridor (085P1000817). This work was supported by grants from the National Science Foundation (MCB 1022010) and the UW College of Agricultural and Life Sciences (Hatch) to R.D.V.
PY - 2013/1/8
Y1 - 2013/1/8
N2 - The phytochrome superfamily encompasses a diverse collection of photochromic photoreceptors in plants and microorganisms that employ a covalently linked bilin cradled in a cGMP-phosphodiesterase/adenylyl-cyclase/ FhlA (GAF) domain to detect light. Whereas most interconvert between red- and far-red-light-absorbing states, cyanobacteria also express variants called cyanobacteriochromes (CBCRs) that modify bilin absorption to collectively perceive the entire visible spectrum. Here, we present two X-ray crystallographic structures of the GAF domain from the blue/green photochromic CBCR PixJ from Thermosynechococcus elongatus. These structures confirm the hypothesis that CBCRs variably manipulate the chromophore π-conjugation system through isomerization and a second thioether linkage, in this case involving the bilin C10 carbon and Cys494 within a DXCF sequence characteristic of blue/green CBCRs. Biochemical studies support a mechanism for photoconversion whereby the second linkage ruptures on route to the green-light-absorbing state. Collectively, the TePixJ(GAF) models illustrate the remarkable structural and photochemical versatility among phytochromes and CBCRs in driving light perception.
AB - The phytochrome superfamily encompasses a diverse collection of photochromic photoreceptors in plants and microorganisms that employ a covalently linked bilin cradled in a cGMP-phosphodiesterase/adenylyl-cyclase/ FhlA (GAF) domain to detect light. Whereas most interconvert between red- and far-red-light-absorbing states, cyanobacteria also express variants called cyanobacteriochromes (CBCRs) that modify bilin absorption to collectively perceive the entire visible spectrum. Here, we present two X-ray crystallographic structures of the GAF domain from the blue/green photochromic CBCR PixJ from Thermosynechococcus elongatus. These structures confirm the hypothesis that CBCRs variably manipulate the chromophore π-conjugation system through isomerization and a second thioether linkage, in this case involving the bilin C10 carbon and Cys494 within a DXCF sequence characteristic of blue/green CBCRs. Biochemical studies support a mechanism for photoconversion whereby the second linkage ruptures on route to the green-light-absorbing state. Collectively, the TePixJ(GAF) models illustrate the remarkable structural and photochemical versatility among phytochromes and CBCRs in driving light perception.
UR - http://www.scopus.com/inward/record.url?scp=84872126119&partnerID=8YFLogxK
U2 - 10.1016/j.str.2012.11.001
DO - 10.1016/j.str.2012.11.001
M3 - Article
C2 - 23219880
AN - SCOPUS:84872126119
SN - 0969-2126
VL - 21
SP - 88
EP - 97
JO - Structure
JF - Structure
IS - 1
ER -