GAF-domain-containing bilin-binding photoreceptor

GAF-domain-containing bilin-binding photoreceptors are a diverse superfamily of light-sensitive proteins found in plants, bacteria, and fungi, characterized by a GAF domain that covalently binds a linear tetrapyrrole (bilin) chromophore. This family includes the well-known phytochromes, which typically sense red and far-red light, and the more recently discovered cyanobacteriochromes, which exhibit a broad spectral range from ultraviolet to near-infrared. Upon light absorption, the bilin chromophore undergoes a reversible 15Z/15E photoisomerization, inducing structural changes in the protein that regulate downstream signaling pathways, such as gene expression and phototaxis. While not traditional therapeutic targets for human disease, these photoreceptors are pivotal in agricultural science and have become essential tools in optogenetics and bioimaging due to their ability to be controlled by long-wavelength light, which offers deep tissue penetration. Their unique photochemical properties allow for the precise, non-invasive manipulation of cellular functions in various research contexts, such as light-triggered gene therapy or protein recruitment. However, their application in mammalian systems often requires the exogenous supply of bilin chromophores, as these are not naturally produced in human cells.

Other names

PhytochromeCyanobacteriochromeCBCRBilin-binding GAF domainBacterial phytochromeBphPCph1Cph2

Light-induced 15Z/15E photoisomerization of a covalently bound bilin chromophore (such as phycocyanobilin or biliverdin) within the GAF domain, triggering a conformational change that modulates the activity of associated signaling domains (e.g., histidine kinase).