Molecular Mechanism in Mobilization of Proton Pump to Apical Cell Membrane of Gastric Parietal Cells

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The molecular mechanism involved in targeting of proton pump molecules to apical cell membrane of gastric parietal cells was studied. The Na-pump that is restricted basolaterally was examined in contrast.1. Assembly of the alpha-and beta-subunits is pre-requisite for targeting of the alpha-subunit to cell membranes. The disulfide-bonded loops in the extracellular domain of the beta-subunit and N-terminal domain of the alpha-subunit are involved in the assembly.2. The beta-subunit is interchangable between proton-and Na-pumps with respect to assembly with the alpha-subunit, but resulting hibrids are functionally inactive.Chimeric beta-subunits were constructed in order to assign specific site (s) of each beta-subunit. The specific sites are distributed in the extracellular domain of the beta-subunit.3. The first disulfide-bonded loop (L_1) in the extracellular domain is one of the specific sites. The 148th amino acid residue within L_1 is especially important.4. These results are summarized in our review.