Characterization of cyanobacteriochrome TePixJ from a thermophilic cyanobacterium Thermosynechococcus elongatus strain BP-1.
A putative photoreceptor gene, TepixJ, of a thermophilic cyanobacterium is homologous to SypixJ1 that mediates positive phototaxis in the unicellular motile cyanobacterium Synechocystis sp. PCC 6803. The putative chromophore-binding GAF domain of TePixJ protein was overexpressed as a fusion with a polyhistidine tag (His-TePixJ_GAF) in Synechocystis cells and isolated to homogeneity. The photoreversible conversion of His-TePixJ_GAF showed peaks at 531, 341 and 266 nm for the green light-absorbing form (Pg form), and peaks at 433 and 287 nm for the blue light-absorbing form (Pb form). At 77K, the Pg form fluoresced at 580 nm, while the Pb form did not emit any fluorescence. Mass spectrometry of the tryptic chromopeptide demonstrated that a phycocyanobilin isomer binds to the conserved cysteine at ring A via a thioether bond. It is established that TePixJ and SyPixJ1 are novel photoreceptors in cyanobacteria ('cyanobacteriochromes') that are similar, but distinct from the phytochromes and bacteriophytochromes.
Ishizuka
Takami
T
Department of Life Sciences (Biology), The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902 Japan.
Shimada
Takashi
T
Okajima
Koji
K
Yoshihara
Shizue
S
Ochiai
Yuriko
Y
Katayama
Mitsunori
M
Ikeuchi
Masahiko
M
D000595:Amino Acid Sequence; D000458:Cyanobacteria / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D020283:Photoreceptors, Microbial / Q000737:chemistry* / Q000235:genetics*; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D020283:Photoreceptors, Microbial