Binding domain of oligomycin on Na+,K+-ATPase

Oligomycin inhibits Na+,K+-ATPase activity by stabilizing the Na+ occlusion but not the K+ occlusion. To locate the binding domain of oligomycin on Na+,K+-ATPase, the tryptic-digestion profile of Na+,K+-ATPase was compared with the profile of Na+ occlusion within the digested Na+,K+-ATPase in the presence of oligomycin. The Na+ occlusion profile is responsible for the digestion profile of the or-subunit, which is the catalytic subunit of the ATPase. The effect of oligomycin on chimeric Ca2+-ATPase activity was examined. The chimera used, in which the 163 N-terminal amino acids of chicken sarcoplasmic/endoplasmic reticulum Ca2+-ATPase 1 were replaced with the 200 N-terminal amino acids of the chicken Na+,K+-ATPase alpha 1-subunit, partially retains the Na+-dependent characteristics of Na+,K+-ATPase, because the chimeric Ca2+-ATPase activity is activated by Na+ but inhibited by ouabain, a specific inhibitor of Na+,K+-ATPase (Ishii, T., Lemas, M.V., Takeyasu, K., 1994, Proc. Natl. Acad. Sci. U. S. A., 91, 6103-6107). Oligomycin depressed the activation by Na+ of the chimeric Ca2+-ATPase activity. These findings suggest that the 200 N-terminal amino acids of the Na+,K+-ATPase alpha-subunit include a binding domain for oligomycin. (C) 2000 Elsevier Science B.V. All rights reserved.