Cyanobacteriochrome


Cyanobacteriochromes are phytochrome-related photoreceptor proteins found only in cyanobacteria.

Molecular characterization

Cyanobacteriochrome covalently binds a linear tetrapyrrole molecule in the GAF domain. The A-ring of linear tetrapyrrole molecule is anchored at cysteine residue in the GAF domain via thioether bond. The GAF domain of cyanobacteriochrome is related to phytochrome GAF, however, These GAF domains are distinct. A second cysteine linkage to the tetrapyrrole is found in some cyanobacteriochrome GAF domains resulting in blue-green photo reversible light sensitivity

Spectral properties

They perform reversible photoconversion between green- and red- absorbing forms or between blue- and green-absorbing forms. These spectral properties significantly differ from that of phytochrome which photoconverts between red- and far-red-absorbing forms.

Examples of cyanobacteriochrome domain containing proteins

One protein, which contains a cyanobacteriochrome as well as a phytochrome-like photosensory module is the protein called "Cph2" from Synechocystis sp. PCC 6803. The phytochrome-like domains switch between a red and a far-red absorbing form, the cyanobacteriochrome domain switches between a green- and a blue-absorbing form.