Fluorescence of phytochrome adducts with synthetic locked chromophores.
We performed steady state fluorescence measurements with phytochromes Agp1 and Agp2 of Agrobacterium tumefaciens and three mutants in which photoconversion is inhibited. These proteins were assembled with the natural chromophore biliverdin (BV), with phycoerythrobilin (PEB), which lacks a double bond in the ring C-D-connecting methine bridge, and with synthetic bilin derivatives in which the ring C-D-connecting methine bridge is locked. All PEB and locked chromophore adducts are photoinactive. According to fluorescence quantum yields, the adducts may be divided into four different groups: wild type BV adducts exhibiting a weak fluorescence, mutant BV adducts with about 10-fold enhanced fluorescence, adducts with locked chromophores in which the fluorescence quantum yields are around 0.02, and PEB adducts with a high quantum yield of around 0.5. Thus, the strong fluorescence of the PEB adducts is not reached by the locked chromophore adducts, although the photoconversion energy dissipation pathway is blocked. We therefore suggest that ring D of the bilin chromophore, which contributes to the extended π-electron system of the locked chromophores, provides an energy dissipation pathway that is independent on photoconversion.
Botanical Institute, Karlsruhe Institute of Technology, Campus South, Kaiserstrasse 2, D-76131 Karlsruhe, Germany.
Benjamin
B
Zienicke
Li-Yi
LY
Chen
Htoi
H
Khawn
Mostafa A S
MA
Hammam
Hideki
H
Kinoshita
Johannes
J
Reichert
Anne S
AS
Ulrich
Katsuhiko
K
Inomata
Tilman
T
Lamparter
D016960:Agrobacterium tumefaciens / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D001664:Biliverdine / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000737:chemistry* / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010777:Photochemistry; D052980:Phycobilins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010799:Phycoerythrin / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010834:Phytochrome / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary
D001426:Bacterial Proteins; D005456:Fluorescent Dyes; D052980:Phycobilins; D010799:Phycoerythrin; D010834:Phytochrome; C011070:phycoerythrobilin; D001664:Biliverdine