Structures of cyanobacteriochromes from phototaxis regulators AnPixJ and TePixJ reveal general and specific photoconversion mechanism

Rei Narikawa, Takami Ishizuka, Norifumi Muraki, Tomoo Shiba, Genji Kurisu, Masahiko Ikeuchi

Research output: Contribution to journalArticlepeer-review

131 Citations (Scopus)


Cyanobacteriochromes are cyanobacterial tetrapyrrole-binding photoreceptors that share a bilin-binding GAF domain with photoreceptors of the phytochrome family. Cyanobacteriochromes are divided into many subclasses with distinct spectral properties. Among them, putative phototaxis regulators PixJs of Anabaena sp. PCC 7120 and Thermosynechococcus elongatus BP-1 (denoted as AnPixJ and TePixJ, respectively) are representative of subclasses showing red-green-type and blue/green-type reversible photoconversion, respectively. Here, we determined crystal structures for the AnPixJ GAF domain in its red-absorbing 15Z state (Pr) and the TePixJ GAF domain in its green-absorbing 15E state (Pg). The overall structure of these proteins is similar to each other and also similar to known phytochromes. Critical differences found are as follows: (i ) the chromophore of AnPixJ Pr is phycocyanobilin in a C5-Z,syn/C10-Z,syn/C15-Z,anti configuration and that of TePixJ Pg is phycoviolobilin in a C10-Z,syn/C15-E,anti configuration, (ii ) a side chain of the key aspartic acid is hydrogen bonded to the tetrapyrrole rings A, B and C in AnPixJ Pr and to the pyrrole ring D in TePixJ Pg, (iii) additional protein-chromophore interactions are provided by subclass-specific residues including tryptophan in AnPixJ and cysteine in TePixJ. Possible structural changes following the photoisomerization of the chromophore between C15-Z and C15-E are discussed based on the X-ray structures at 1.8 and 2.0-Å resolution, respectively, in two distinct configurations.

Original languageEnglish
Pages (from-to)918-923
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number3
Publication statusPublished - 2013 Jan 15
Externally publishedYes


  • Back-to-back dimer
  • Chemotaxis
  • Methyl accepting

ASJC Scopus subject areas

  • General


Dive into the research topics of 'Structures of cyanobacteriochromes from phototaxis regulators AnPixJ and TePixJ reveal general and specific photoconversion mechanism'. Together they form a unique fingerprint.

Cite this