Potassium ion binding site on H+,K+-ATPase

The potassium ion (K⁺) binding site is a critical functional region of the H⁺,K⁺-ATPase enzyme, a P-type ATPase exchanging protons (H⁺) and potassium ions across cellular membranes. This exchange is essential for gastric acid secretion in the stomach and ion homeostasis in the kidney. The K⁺ binding site enables the enzyme to bind extracellular potassium ions during its catalytic cycle, triggering conformational changes that allow release of protons into the lumen and subsequent transport of K⁺ into the cytoplasm. Certain drugs, known as "potassium competitive acid blockers" (PCABs), inhibit gastric acid secretion by blocking access or function at this location.

Inhibition of K+ binding and H+/K+ exchange, leading to reduced gastric acid secretion.