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Title: The proton pump inhibitor, E3810, binds to the N-terminal half of the alpha-subunit of gastric H+,K(+)-ATPase. Author: Morii M, Hamatani K, Takeguchi N. Journal: Biochem Pharmacol; 1995 Jun 16; 49(12):1729-34. PubMed ID: 7598734. Abstract: E3810 (2-([4-(3-methoxypropoxy)-3-methylpyridine-2-yl]methylsulphinyl )- 1H-benzimidazole sodium salt), an inhibitor of gastric proton pump (gastric H+,K(+)-ATPase), is activated in a luminal acidic environment of gastric glands and binds to a Cys residue of H+,K(+)-ATPase on its luminal side. It was found that bound E3810 is transformed into a strongly fluorescent compound by UV-light irradiation (excitation wavelength = 335 nm, emission wavelength = 470 nm). The location of Cys residue bound with E3810 in the alpha-subunit of hog gastric H+,K(+)-ATPase was estimated from the fluorescence labelling and limited tryptic digestion of the enzyme. Tryptic digestion in the presence of Mg-ATP produces N-terminal 67 kDa subfragment which contains the phosphorylation and fluorescein 5'-isothiocyanate binding sites and C-terminal 35 kDa subfragment. Trypsin digestion in the presence of KCl produces N-terminal 42 kDa and C-terminal 56 kDa subfragments. E3810 was found to bind to both N-terminal but not to any of two C-terminal subfragments. Taking the amino acid sequence and topology of this ATPase as well as the fact that the ratio of specific binding sites per alpha-subunit is one into consideration, the possibility that E3810 specifically binds to Cys322 residue of hog gastric H+,K(+)-ATPase is discussed.[Abstract] [Full Text] [Related] [New Search]