The tripartite modular organization of group 4 hydrogenase could be found in many archaeal genomes, however, there is no report to unveil the physiological role of multisubunit monovalent cation/proton antiporter participating in mediating the electron relay of the respiratory chain to date. Here, we try to address the identity of chemiosmotic ion to couple formate oxidation to ATP synthesis in the anaerobic respiratory mechanism of formate oxidation. Additionally, the physiological role of the multisubunit monovalent cation/proton antiporter related with ATP synthesis was considered.the electron relay of the respiratory chain to date. Here, we try to address the identity of chemiosmotic ion to couple formate oxidation to ATP synthesis in the anaerobic respiratory mechanism of formate oxidation. Additionally, the physiological role of the multisubunit monovalent cation/proton antiporter related with ATP synthesis was considered.1