gastric H+/K+ ATPase (H+ transporting ATPase, K+ transporting ATPase, proton pump)

Function: - catalyzes hydrolysis of ATP coupled with exchange of H⁺ & K⁺ ions across the plasma membrane - responsible for acid production in the stomach - secretes HCl; 900 fold H⁺ gradient obtained via hydrolysis of ATP Inhibition: - proton pump inhibitors (direct inhibition) - H2 receptor antagonists (indirect inhibition) ATP + H₂O + H⁺(in) + K⁺(out) ADP + phosphate + H⁺(out) + K⁺(in) Structure: - composed of two subunits: alpha (catalytic) & beta

General

E1-E2 ATPase or P-type ATPase multisubunit protein plasma membrane protein regulatory molecule

Properties

COMPARTMENT: plasma membrane MOTIF: membrane region active site MOTIF: adenine nucleotide-binding site Asp phosphorylation site SUBUNITS: gastric H+/K+ ATPase alpha MOTIF: cytoplasmic domain {2-98} transmembrane domain {99-119} exoplasmic loop {120-142} transmembrane domain {143-163} cytoplasmic loop {164-299} transmembrane domain {300-319} exoplasmic loop {320-331} transmembrane domain {332-349} cytoplasmic loop {350-783} MOTIF: aspartate residue {D387} Mg+2-binding site SITE: 728-728 Mg+2-binding site SITE: 732-732 transmembrane domain {784-803} exoplasmic loop {804-813} transmembrane domain {814-834} cytoplasmic loop {835-854} transmembrane domain {855-877} exoplasmic loop {878-929} transmembrane domain {930-949} cytoplasmic loop {950-963} MOTIF: Ser phosphorylation site {S954} transmembrane domain {964-982} exoplasmic loop {983-997} transmembrane domain {998-1018} cytoplasmic domain {1019-1035} gastric H+/K+ ATPase beta MOTIF: transmembrane domain {37-57} N-glycosylation site {N99} N-glycosylation site {N103} N-glycosylation site {N130} cysteine residue {C131} MODIFICATION: cysteine residue {C152} N-glycosylation site {N146} cysteine residue {C152} MODIFICATION: cysteine residue {C131} N-glycosylation site {N161} cysteine residue {C162} MODIFICATION: cysteine residue {C178} cysteine residue {C178} MODIFICATION: cysteine residue {C162} N-glycosylation site {N193} cysteine residue {C201} MODIFICATION: cysteine residue {C263} N-glycosylation site {N222} cysteine residue {C263} MODIFICATION: cysteine residue {C201}

References

Textbook of Medical Physiology, 8th ed., AC Guyton, WB Saunders, Philadelphia, 1991, pg 336

Components

gastric H+/K+ ATPase alpha subunit (K+ transporting ATPase alpha chain 1, ATP4A) gastric H+/K+ ATPase beta subunit (K+-transporting ATPase subunit beta, proton pump beta chain, ATP4B)