A Novel Photoactive GAF Domain of Cyanobacteriochrome AnPixJ That Shows Reversible Green/Red Photoconversion

• Published in: Journal of molecular biology 2008-07, Vol.380 (5), p.844-855
• Main Authors: Narikawa, Rei, Fukushima, Yoshimasa, Ishizuka, Takami, Itoh, Shigeru, Ikeuchi, Masahiko
• Format: Article
• Language: English
• Subjects: Alanine - metabolism; Amino Acid Sequence; Amino Acid Substitution; Anabaena; Anabaena - chemistry; cyanobacteriochrome; Cyanophyta; Escherichia coli; Escherichia coli - genetics; GAF domain; Histidine - metabolism; Hydrogen-Ion Concentration; Light; lumi-R; Molecular Sequence Data; Molecular Structure; Nostoc; Photoreceptor Cells - chemistry; Photoreceptor Cells - metabolism; Photoreceptor Cells - radiation effects; Photosynthetic Reaction Center Complex Proteins - genetics; Photosynthetic Reaction Center Complex Proteins - metabolism; Photosynthetic Reaction Center Complex Proteins - radiation effects; phototaxis; Phycobilins - metabolism; Phycocyanin - metabolism; phytochrome; Phytochrome - chemistry; Phytochrome - genetics; Phytochrome - isolation & purification; Phytochrome - metabolism; Protein Denaturation; Protein Structure, Tertiary; Sequence Homology, Amino Acid; Spectrophotometry, Ultraviolet; Urea - pharmacology
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2008.05.035

We report the discovery of a novel cyanobacteriochrome, the green/red photoreceptor AnPixJ (All1069), isolated from the heterocyst-forming cyanobacterium Anabaena ( Nostoc) sp. PCC 7120. Cyanobacteriochromes are a recently emerging tetrapyrrole-based photoreceptor superfamily that are distantly related to the conventional red/far-red photoreceptor phytochromes (Phys). The chromophore-binding domains of AnPixJ produced in cyanobacterial and Escherichia coli cells both showed a reversible and full photoconversion between a green-absorbing form (λ max = 543 nm) and a red-absorbing form (λ max = 648 nm). Denaturation analysis revealed that the green-absorbing form and the red-absorbing form covalently ligated phycocyanobilin with E-configuration and Z-configuration at the C15 C16 double bond, respectively. Time-resolved spectral analysis showed the formation of the first intermediate state peaking at 680 nm from the dark-stable red-absorbing form. This step resembles the first photoconversion step from the red-absorbing form to the red-shifted lumi-R intermediate state of the Phys. These results suggest that the Pr of AnPixJ is almost equivalent to that of the Phys and starts a primary photoreaction with Z-to- E isomerization in a mechanism similar to that in the Phys, but is finally photoconverted to the unique green-absorbing form.