Difference between the E1 and E2 conformations of gastric H⁺/K⁺‐ATPase in a multilamellar lipid film system

Abstract

A liquid flow cell was used for an attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) study of conformational changes taking place in the gastric H+/K+-ATPase. Shifting from E1 to E2 form is induced by replacing Na+ by K+ ions. Introducing ions through a flow passing over a protein multilayer film induced the conformational change without cell manipulations. Measurement sensitivity was thereby improved by about one order of magnitude. The detection threshold allowed the possibility to detect a change affecting five amino acids out of the 1324 that compose the H+/K+-ATPase molecule. It appeared that fewer than five amino-acid residues undergo a conformational change upon replacing Na+ by K+ ions in the medium. Evidence that conformational changes occur in an identical system was brought by monitoring the fluorescence of fluorescein isothiocyanate-labeled H+/K+-ATPase in similar conditions. Our data suggest that essentially the tertiary structure of the protein is modified.

Clinical significance of P‑class pumps in cancer (Review)

“…The HKA is a heterodimer composed of two subunits, α and β, which are expressed by two separate genes (ATP4A, ATP4B) ( 90 ). The ATP4A gene encodes for the gastric α subunit, composed of 10 transmembrane helices and housing the pump inhibitor-binding site intracellularly, known as cysteine 813.…”