Halorhodopsins

Halorhodopsins are a family of light-driven ion pumps found in halobacteria and some archaea. These membrane proteins are responsible for light-induced chloride transport across the cell membrane. Upon absorbing light, the retinal chromophore within the halorhodopsin undergoes a series of conformational changes, leading to the translocation of chloride ions. This process is crucial for maintaining the osmotic balance and electrochemical gradient within the cell, particularly in environments with high salt concentrations. Halorhodopsins are distinct from rhodopsins, which are primarily involved in light sensation. While both are photoreceptor proteins containing retinal, their functions and ion transport mechanisms differ significantly. The structure of halorhodopsin is characterized by seven transmembrane helices, a common motif for many membrane proteins. Researchers have utilized halorhodopsins as tools in optogenetics, engineering them for light-controlled neuronal activity due to their ability to hyperpolarize cells by pumping chloride ions inwards. This application has opened new avenues for studying and manipulating neural circuits.