title: Low-affinity Na+ sites on (Na+ +K+)-ATPase modulate inhibition of Na+-ATPase activity by vanadate.
abstract: Na+-ATPase activity is extremely sensitive to inhibition by vanadate at low Na+ concentrations where Na+ occupies only high-affinity activation sites. Na+ occupies low-affinity activation sites to reverse inhibition of Na+-ATPase and (Na+, K+)-ATPase activities by vanadate. This effect of Na+ is competitive with respect to both vanadate and Mg2+. The apparent affinity of the enzyme for vanadate is markedly increased by K+. The principal effect of K+ may be to displace Na+ from the low-affinity sites at which it activates Na+-ATPase activity.
mesh_terms: D000818:Animals; D001665:Binding Sites; D004285:Dogs; D007679:Kidney Medulla / Q000201:enzymology*; D007700:Kinetics; D011485:Protein Binding; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology*
chemical_list: D014639:Vanadium; D014638:Vanadates; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase