Conformational rearrangement of gastric H+,K+-ATPase induced by an acid suppressant

Acid-related gastric diseases are associated with disorder of digestive tract acidification. The gastric proton pump, H+,K+-ATPase, exports H+ in exchange for luminal K+ to generate a highly acidic environment in the stomach, and is a main target for acid suppressants. Here, we report the three-dimensional structure of gastric H+, K+-ATPase with bound SCH28080, a representative K+-competitive acid blocker, at 7 angstrom resolution based on electron crystallography of two-dimensional crystals. The density of the bound SCH28080 is found near transmembrane (TM) helices 4, 5 and 6, in the luminal cavity. The SCH28080-binding site is formed by the rearrangement of TM helices, which is in turn transmitted to the cytoplasmic domains, resulting in a luminal-open conformation. These results represent the first structural evidence for a binding site of an acid suppressant on H+, K+-ATPase, and the conformational change induced by this class of drugs.