Keiichi Kojima, Tetsuya Ueta, Tomoyasu Noji, Keisuke Saito, Kanae Kanehara, Susumu Yoshizawa, Hiroshi Ishikita and Yuki Sudo. Vectorial Proton Transport Mechanism of RxR, a Phylogenetically Distinct and Thermally Stable Microbial Rhodopsin. Scientific Reports, 10:282. (2020)