Light-driven proton pump. May have a regulatory rather than energy harvesting function, based on light-induced opening of proton channels, to modulate cell physiology depending on light intensity variations. Could be, therefore, a sensory rhodopsin, potentially associated with a transducer component. Contains one covalently linked retinal chromophore. Presents a much slower photocycle than that of the green-absorbing proteorhodopsin, probably an adaptation to the intensity of solar illumination at a depth of 75m, where this bacterium was collected. Transport occurs only at pHs above 7 and is unidirectional. Belongs to the archaeal/bacterial/fungal opsin family.