AR3 is expressed by Halorubrum sodomense. The organism was first identified in the Dead Sea in 1980 and requires a higher concentration of Mg ions for growth than related halophiles. The aop3 gene was cloned by Ihara and colleagues at Nagoya University in 1999 and the protein was found to share 59% sequence identity with bacteriorhodopsin. The crystal structure of AR3 was solved by Anthony Watts at Oxford University and Isabel Moraes at the National Physical Laboratory, together with collaborators at Diamond Light Source.
Mutants of Archaerhodopsin-3 (AR3) are widely used as tools in optogenetics for neuroscience research.
AR3 has recently been introduced as a fluorescent voltage sensor.