Cyanobacteriochromes (CBCRs) are phytochrome-related photoreceptors identified in cyanobacteria.In contrast to canonical phytochromes,however,CBCRs are not composed by the common PAS-GAF-PHY motif,but instead they are composed of several aligned GAF domains,of which one or some bind phycocyanobilin (PCB) as photochemically active chromophore.