Bioinformatic Study of Possible Acute Regulation of Acid Secretion in the Stomach

The gastric H⁺,K⁺-ATPase is an integral membrane protein which derives energy from the hydrolysis of ATP to transport H⁺ ions from the parietal cells of the gastric mucosa into the stomach in exchange for K⁺ ions. It is responsible for the acidic environment of the stomach, which is essential for digestion. Acid secretion is regulated by the recruitment of the H⁺,K⁺-ATPase from intracellular stores into the plasma membrane on the ingestion of food. The similar amino acid sequences of the lysine-rich N-termini α-subunits of the H⁺,K⁺- and Na⁺,K⁺-ATPases, suggests similar acute regulation mechanisms, specifically, an electrostatic switch mechanism involving an interaction of the N-terminal tail with the surface of the surrounding membrane and a modulation of the interaction via regulatory phosphorylation by protein kinases. From a consideration of sequence alignment of the H⁺,K⁺-ATPase and an analysis of its coevolution with protein kinase C and kinases of the Src family, the evidence points towards a phosphorylation of tyrosine-7 of the N-terminus by either Lck or Yes in all vertebrates except cartilaginous fish. The results obtained will guide and focus future experimental research.