Involvement of the H3O+-Lys-164 -Gln-161-Glu-345 Charge Transfer Pathway in Proton Transport of Gastric H+,K+-ATPase

Morii, Magotoshi; Yamauchi, Masashi; Ichikawa, Tomohiko; Fujii, Takuto; Takahashi, Yûji; Asano, Shinji; Takeguchi, Noriaki; Sakai, Hideki

doi:10.1074/jbc.m800563200

Cited by 20 publications

(11 citation statements)

References 39 publications

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“…This catalytic subunit consists of 1033 or 1034 amino acids with 10 transmembrane segments in all species. Functional studies demonstrated that ATP catalyzed an electroneutral exchange of H for K, with a variable stoichiometry of 2H/2K/ATP at pH 6.1, which fell to 1H/1K/ATP as luminal pH fell below 3.0 [9–11]. The β subunit consists of 291 amino acids and contains six or seven N-linked glycosylation sites with one trans-membrane segment [12–14].…”

Section: The Gastric Hk-atpasementioning

confidence: 99%

“…The potassium occlusion site shows distorted octahedral geometry, with K + bound predominantly on the M4 helix, with ligands contributed by backbone carbonyl oxygens of V338, A339, and V341, and by side chain oxygens of E820 and E795 [18•]. Recently two hydronium transporting pathways were proposed [11]. The hydroniums in the binding sites are transported into the lumen during the conformational transition from E 1 P to E 2 P.…”

Section: The Gastric Hk-atpasementioning

confidence: 99%

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Pharmacology of proton pump inhibitors

Shin

Sachs

2008

Curr Gastroenterol Rep

381

329

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The gastric H,K-ATPase is the primary target for the treatment of acid-related diseases. Proton pump inhibitors (PPIs) are weak bases composed of two moieties, a substituted pyridine with a primary pK a of about 4.0, which allows selective accumulation in the secretory canaliculus of the parietal cell, and a benzimidazole with a second pK a of about 1.0. PPIs are acid-activated prodrugs that convert to sulfenic acids or sulfenamides that react covalently with one or more cysteines accessible from the luminal surface of the ATPase. Because of covalent binding, their inhibitory effects last much longer than their plasma half-life. However, the short half-life of the drug in the blood and the requirement for acid activation impair their efficacy in acid suppression, particularly at night. PPIs with longer half-life promise to improve acid suppression. All PPIs give excellent healing of peptic ulcers and produce good results in reflux esophagitis. PPIs combined with antibiotics eradicate Helicobacter pylori.

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Section: The Gastric Hk-atpasementioning

confidence: 99%

Section: The Gastric Hk-atpasementioning

confidence: 99%

Pharmacology of proton pump inhibitors

Shin

Sachs

2008

Curr Gastroenterol Rep

381

329

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“…5B) which may undergo fast deprotonation as suggested by molecular dynamic simulations of the H + -binding site of ATP-synthase [55]. However, more efficient H + transport by E803Q mutant ATPase suggest that hydronium ions may be the ionic species to be transported, as it was proposed previously for the gastric H + , K + -ATPase [56–57]. Homology modeling of the yeast pump with the Ca 2+ -ATPase also showed that two hydronium ions could be bound and transported by the yeast enzyme (Fig 5A) [24].…”

Section: Discussionmentioning

confidence: 82%

Structure–function relationships in membrane segment 6 of the yeast plasma membrane Pma1 H+-ATPase

Miranda

Pardo

Петров

2011

Biochimica et Biophysica Acta (BBA) - Biomembranes

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The crystal structures of the Ca2+- and H+-ATPases shed light into the membrane embedded domains involved in binding and ion-translocation. Consistent with site-directed mutagenesis, these structures provided additional evidence that membrane-spanning segments M4, M5, M6 and M8 are the core through which cations are pumped. In the present study, we have used alanine/serine scanning mutagenesis to study the structure-function relationships within M6 (Leu-721-Pro-742) of the yeast plasma membrane ATPase. Of the 22 mutants expressed and analyzed in secretory vesicles, alanine substitutions at two well conserved residues (Asp-730 and Asp-739) led to a complete block in biogenesis; in the mammalian P-ATPases, residues corresponding to Asp-730 are part of the cation-binding domain. Two other mutants (V723A and I736A) displayed a dramatic 20 fold increase in the IC50 for inorganic orthovanadate compared to the wild-type control, accompanied by a significant reduction in the Km for Mg-ATP, and an alkaline shift in the pH optimum for ATP hydrolysis. This behavior is apparently due to a shift in equilibrium from the E2 conformation of the ATPase towards the E1 conformation. By contrast, the most striking mutants lying toward the extracellular side in a helical structure (L721A, I722A, F724A, I725A, I727A and F728A), were expressed in secretory vesicles but had a severe reduction of ATPase activity. Moreover, all of these mutants but one (F728A) were unable to support yeast growth when the wild-type chromosomal PMA1 gene was replaced by the mutant allele. Surprisingly, in contrast to M8 where mutations S800A and E803Q (Guerra, G. et al., Biochim. Biophys. Acta 1768: 2383–2392, 2007) led to a dramatic increase in the apparent stoichiometry of H+ transport, three substitutions (A726S, A732S and T733A) in M6 showed a reduction in the apparent coupling ratio. Taken together, these results suggest that M6 residues play an important role in protein stability and function, and probably are responsible for cation binding and stoichiometry of ion transport as suggested by homology modeling.

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“…Furthermore, differences could be related to differences in transport mechanism due to the particular status of protons as the transported species. A dimeric state, for instance, might facilitate transfer through the membrane, either as the hydronium ion, H 3 O ϩ , by the Grothuiss effect, or as H ϩ by a protein wire mechanism (42). In order to address these questions, we have in the present work attempted to apply our experience on the use of surfactants for solubilization of functionally active membrane proteins to H ϩ ,K ϩ -ATPase in conjunction with structural studies by analytical ultracentrifugation and other advanced biophysical techniques (43).…”

mentioning

confidence: 99%