Cation Selectivity of Gastric H,K-ATPase and Na,K-ATPase Chimeras

Blostein, Rhoda; Dunbar, Lisa A.; Mense, Martin; Scanzano, Rosemarie; Wilczynska, Ania; Caplan, Michael J.

doi:10.1074/jbc.274.26.18374

Cited by 19 publications

(29 citation statements)

References 30 publications

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“…Indeed, many reports demonstrate that regions outside the proposed occlusion pocket influence the cation selectivity (31)(32)(33)(34). In the present study we shed some light on the regions involved in the cation specificity of Na ϩ ,K ϩ -ATPase and H ϩ ,K ϩ -ATPase.…”

Section: Discussionmentioning

confidence: 77%

“…In the past decade, it has been demonstrated that the predicted transmembrane segments 4 -6 are involved in cation occlusion (35). Recently, Mense et al (34) (33) suggested that both the N-terminal half of the intracellular M4-M5 loop and the adjacent transmembrane helice(s) of Na ϩ ,K ϩ -ATPase and H ϩ ,K ϩ -ATPase play a role in cation selectivity. Chimera HN16 includes all these fragments, except Val 898 -Ile 953 .…”

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confidence: 99%

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Chimeras of X+,K+-ATPases

Koenderink

Swarts

Stronks

et al. 2001

Journal of Biological Chemistry

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In this study we reveal regions of Na+,K+-ATPase and H+,K+-ATPase that are involved in cation selectivity. A chimeric enzyme in which transmembrane hairpin M5-M6 of H+,K+-ATPase was replaced by that of Na+,K+-ATPase was phosphorylated in the absence of Na+and showed no K+-dependent reactions. Next, the part originating from Na+,K+-ATPase was gradually increased in the N-terminal direction. We demonstrate that chimera HN16, containing the transmembrane segments one to six and intermediate loops of Na+,K+-ATPase, harbors the amino acids responsible for Na+specificity. Compared with Na+,K+-ATPase, this chimera displayed a similar apparent Na+affinity, a lower apparent K+affinity, a higher apparent ATP affinity, and a lower apparent vanadate affinity in the ATPase reaction. This indicates that theE2K form of this chimera is less stable than that of Na+,K+-ATPase, suggesting that it, like H+,K+-ATPase, de-occludes K+ions very rapidly. Comparison of the structures of these chimeras with those of the parent enzymes suggests that the C-terminal 187 amino acids and the β-subunit are involved in K+occlusion. Accordingly, chimera HN16 is not only a chimeric enzyme in structure, but also in function. On one hand it possesses the Na+-stimulated ATPase reaction of Na+,K+-ATPase, while on the other hand it has the K+occlusion properties of H+,K+-ATPase.

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Section: Discussionmentioning

confidence: 77%

mentioning

confidence: 99%

Chimeras of X+,K+-ATPases

Koenderink

Swarts

Stronks

et al. 2001

Journal of Biological Chemistry

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“…This lysine substitutes for a serine present in the Na,K ATPase isoforms. Site-directed mutagenesis of residues of the Na,K ATPases [36,37], the SR Ca ATPase [38] and the H,K ATPase [27,35,39] showed that the ion-binding domain and other features of the gastric ATPase were similar to the Na,K and SERCA Ca ATPases.…”

Section: Secondary Structurementioning

confidence: 99%

Molecular mechanisms in therapy of acid-related diseases

Shin

Vagin

Munson

et al. 2007

Cell. Mol. Life Sci.

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Inhibition of gastric acid secretion is the mainstay of the treatment of gastroesophageal reflux disease and peptic ulceration; therapies to inhibit acid are among the best-selling drugs worldwide. Highly effective agents targeting the histamine H2 receptor were first identified in the 1970s. These were followed by the development of irreversible inhibitors of the parietal cell hydrogenpotassium ATPase (the proton pump inhibitors) that inhibit acid secretion much more effectively. Reviewed here are the chemistry, biological targets and pharmacology of these drugs, with reference to their current and evolving clinical utilities. Future directions in the development of acid inhibitory drugs include modifications of current agents and the emergence of a novel class of agents, the acid pump antagonists.

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“…As proposed by James et al (28) The T345A replacement likely decreases apparent K ϩ affinity by directly affecting the cation binding pocket. Although the cation binding sites of the sodium pump are located within the transmembrane segments, earlier studies, such as our H,K/ Na,K-ATPase chimera experiments, showed that a portion of the M4-M5 loop juxtaposed to the stalk segment leading to M4-affected cation selectivity (29). Furthermore, based on the alignment of the amino acid sequence of the Na,K-ATPase with the homologous sarco(endo)plasmic reticulum Ca 2ϩ -ATPase pump and with a known crystal structure, Thr-345 is located in stalk segment 4 within three residues of the plasma membrane (30,31), at least in the E 1 conformational state.…”

Section: Figmentioning

confidence: 99%

Kinetic Alterations due to a Missense Mutation in the Na,K-ATPase α2 Subunit Cause Familial Hemiplegic Migraine Type 2

Segall

Scanzano

Kaunisto

et al. 2004

Journal of Biological Chemistry

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A number of missense mutations in the ATP1A2 gene, which encodes the Na,K-ATPase ␣2 subunit, have been identified in familial hemiplegic migraine with aura. Loss of function and haploinsufficiency have been the suggested mechanisms in mutants for which functional analysis has been reported. This paper describes a kinetic analysis of mutant T345A, recently identified in a detailed genetic analysis of a large Finnish family (Kaunisto, M. A., Harno, H., Vanmolkot, K. R., Gargus, J. J., Sun, G., Hamalainen, E., Liukkonen, E., Kallela, M., van den Maagdenberg, A. M., Frants, R. R., Farkkila, M., Palotie, A., and Wessman, M. (2004) Neurogenetics 5, 141-146). Introducing T345A into the conserved rat ␣2 enzyme does not alter cell growth or catalytic turnover but causes a substantial decrease in apparent K ؉ affinity (2-fold increase in K 0.5(K ؉ ) ). In view of the location of Thr-345 in the cytoplasmic stalk domain adjacent to transmembrane segment 4, the 2-fold increase in K 0.5(K ؉ ) is probably due to T345A replacement altering K ؉ occlusion/deocclusion. Faster K ؉ deocclusion of the mutant via the E 2 (K) ؉ ATP 3 E 1 ⅐ATP ؉ K ؉ partial reaction is evidenced in (i) a marked increase (300%) in K ؉ stimulation of Na-ATPase at micromolar ATP, (ii) a 4-fold decrease in K ATP , and (iii) only a modest increase (ϳ3-fold) in I 50 for vanadate, which was used as a probe of the steady state E 1 /E 2 conformational equilibrium. We suggest that the decreased apparent K ؉ affinity is the basis for a reduced rate of extracellular K ؉ removal, which delays the recovery phase of nerve impulse transmission in the central nervous system and, thereby, the clinical picture of migraine with aura. This is the first demonstration of a mutation that leads to a disease associated with a kinetically altered but fully functional Na,K-ATPase, refining the molecular mechanism of pathogenesis in familial hemiplegic migraine.Familial hemiplegic migraine (FHM) 1 is a rare autosomal dominant form of migraine with aura. This disorder is usually associated with hemiparesis and can be accompanied with clinical features ranging from ataxia to epileptic seizures. This genetically heterogeneous disease has been traced to at least two loci, FHM1 and FHM2. FHM1, which accounts for over 50% of all FHM families, has been traced to chromosome 19p13 and associated with missense mutations in the CACNA1A gene encoding the ␣1 subunit of the voltage-dependent neuronal (P/Q type) calcium channel. A recent breakthrough in migraine genetics is the discovery of missense mutations in the ATP1A2 gene on chromosome 1q23 that encodes the ␣2 isoform of the Na,K-ATPase. This finding gives strong support to the notion that FHM is caused by disruption of normal cation transport. The Na,K-ATPase is an integral membrane protein complex that comprises a large catalytic ␣ subunit of ϳ110 kDa as well as a smaller, highly glycosylated ␤ subunit that ensures the proper folding and mooring of ␣ in the plasma membrane. This P-type ion pump catalyzes the ATP-driven exchange of intrace...

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Cation Selectivity of Gastric H,K-ATPase and Na,K-ATPase Chimeras

Cited by 19 publications

References 30 publications

Chimeras of X+,K+-ATPases

Chimeras of X+,K+-ATPases

Molecular mechanisms in therapy of acid-related diseases

Kinetic Alterations due to a Missense Mutation in the Na,K-ATPase α2 Subunit Cause Familial Hemiplegic Migraine Type 2

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