Proton Extrusion Model (A Billiard model) (IMAGE)

Nagoya University

Proton Extrusion Model (A Billiard model)

Caption

Unusually tight coordination of two glutamates (Glu795 and Glu820) and a lysine (Lys791) at the cation binding site was revealed in the crystal structure. A single H+ bound to Glu820 is extruded by the positive charge of Lys791, even for the highly acidic gastric lumen (left). This mechanism is likened to a billiard model (right). A positive charge at the lysine residue acts as a "cue" that shoots the "yellow ball" (H+) at Glu820. This yellow ball in turn strikes another H+ (green ball) at Glu795 which is exposed to the cation transport pathway. Finally, a single ball (H+) is in the pocket (exit to the gastric lumen).

Credit

Kazuhiro Abe

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