Allows to use formate as major electron donor during aerobic respiration. Subunit alpha possibly forms the active site. formate + NAD(+) = CO2 + NADH Binds 1 molybdenum-bis(molybdopterin guanine dinucleotide) (Mo-bis-MGD) cofactor per subunit. Binds 1 [4Fe-4S] cluster. Formate dehydrogenase is a membrane-bound complex, formed by subunits alpha, beta and gamma. Exported by the Tat system. The position of the signal peptide cleavage has not been experimentally proven. Belongs to the prokaryotic molybdopterin-containing oxidoreductase family.