Ouabain is an inhibitor of which ion pump?
Ouabain is a cardenolide steroid with rhamnose sugar derived from Strophanthus and Acocanthera, historically used as arrow poison and experimentally as specific probe. Pharmacologically it exhibits extremely high affinity for extracellular side of Na+/K+ ATPase, nanomolar Ki, interacting with residues in transmembrane helices M1-M6 and extracellular loops forming ouabain binding pocket accessible only in E2P conformation when outward gate open. Binding stabilizes E2P state, prevents dephosphorylation and return to E1, blocking cycle. Resultant inhibition halts sodium extrusion, intracellular s
Ref: Lingrel and Kuntzweiler, JBC, Ouabain Binding Site and Specific Inhibition of Na+/K+ ATPase.
