In this paper a detailed study of the effect of nitration of tyrosine residues by tetranitromethane on H+ conduction and other reactions catalyzed by the H+ -ATPase complex in phosphorylating submitochondrial particles, uncoupled particles, and the purified complex is presented. Tetranitromethane treatment of submitochondrial particles results in marked inhibition of ATP hydrolysis, ATP-33Pi exchange, and proton conduction by the H+ -ATPase complex. These effects are caused by nitration of tyrosine residues of H+ -ATPase complex as shown by the appearance of the absorption peak at 360 nm (specific for nitrotyrosine formation) and inhibition of ATP hydrolysis and ATP-33Pi exchange in the complex purified from tetranitromethane-treated particles. H+ conduction in phospholipid vesicles inlaid with F0 is also inhibited by tetranitromethane treatment. These observations indicate that tyrosine residue(s) of F0 are critically involved in energy-linked proton translocation in the ATP-ase complex.