3.E.1.4.4
Acetaularia rhodopsin I, ARI or c102333 of 246 aas.  It exhibits outward H⁺ pumping activity, and D89 and D100 are essential for pumping activity (Lee et al. 2015). Blue-light causes a shunt of the photocycle under H⁺ reuptake from the extracellular side (Tsunoda et al. 2006). Similarities and differences of AR with BR have been revealed by detailed electrophysiological studies, revealing among other things, the voltage dependencies of the pump (Tsunoda et al. 2006).