*Cyanobacterial Phytochromes in Optogenetics DOI: http://dx.doi.org/10.5772/intechopen.97522*

Generally, the cyanobacterial chromophore is ligated with cysteine residue but it lacks the chromophore-tied Cys residue is parallel to other CikA homologs. Interconnection between the C-terminal pseudo-receiver domain and quinone is essential for the phase synchronizing of the rhythms [21]. CikA GAF domain of *Synechococcus* is comparable to the SyCikA\_GAF of *Synechocystis* sp. PCC 6803. The properties of SyCikA are extremely uncommon however appear to be viable with the idea of circadian rhythms.
