Sodium pump-mediated ATP:ADP exchange. The sided effects of sodium and potassium ions.

Kaplan, Jack H.

doi:10.1085/jgp.80.6.915

Cited by 42 publications

(28 citation statements)

References 47 publications

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“…This initial phase of activation is due to Na ϩ binding at high affinity cytoplasmic sites; it is followed by a plateau or slight inhibition as Na ϩ is further increased to Ϸ10 mM (27)(28)(29). This inhibitory phase due to Na ϩ ions acting at high affinity extracellular sites (28, 29) is followed by a further increase in activity as the Na ϩ concentration is raised above Ϸ20 mM due to Na ϩ acting as K ϩ congeners at extracellular activation sites (30).…”

Section: Fig 6 Effect Of Namentioning

confidence: 99%

Evidence That Ser775 in the α Subunit of the Na,K-ATPase Is a Residue in the Cation Binding Pocket

Blostein¹,

Wilczynska²,

Karlish³

et al. 1997

Journal of Biological Chemistry

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؉ activation of both the mutant and control enzymes. In this case, the mutant was more sensitive to inhibition. With vanadate as a probe of conformation, a difference in conformational equilibrium between the mutant and control enzymes could not be detected under turnover conditions (Na ؉ -ATPase) in the absence of K ؉ . These results indicate that the increase in apparent affinity for ATP effected by the Ser 775 3 Ala mutation is secondary to a change in intrinsic cation affinity/selectivity. The large change in affinity for extracellular K ؉ compared with cytoplasmic Na ؉ and to Br 2 TITU binding supports the conclusion that the serine hydroxyl is either part of the K ؉ -gate structure or a direct cation-ligating residue that is shared by at least one Na ؉ ion, albeit with less consequence on rate constants for Na ؉ binding or release compared with K ؉ .

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Section: Fig 6 Effect Of Namentioning

confidence: 99%

Evidence That Ser775 in the α Subunit of the Na,K-ATPase Is a Residue in the Cation Binding Pocket

Blostein¹,

Wilczynska²,

Karlish³

et al. 1997

Journal of Biological Chemistry

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“…This work led to the application of the photorelease approach to the study ofthe mechanism ofa wide range of ATP-dependent processes, including the ion-transporting ATPases (7)(8)(9)(10)(11)(12) and muscle contraction (13,14), and it has been used for time-resolved structural studies of the sarcoplasmic reticulum Ca2`pump (15) and of time-resolved structural changes during contraction in muscle fibers (16). The application of the photorelease of "caged" compounds has subsequently been extended to include cyclic nucleotides (17), other nucleotides (18) The publication costs of this article were defrayed in part by page charge payment.…”

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confidence: 99%

Photolabile chelators for the rapid photorelease of divalent cations.

Kaplan

Ellis‐Davies

1988

Proc. Natl. Acad. Sci. U.S.A.

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The properties of a recently synthesized photolabile chelator for divalent cations are described, the affinty of which for Ca2+ changes by some 5 orders of magnitude on illumination. The compound 1-(2-nitro-4,5-dimethoxyphenyl)-N,N,N',N'-tetrakis [(oxycarbonyl) 5). To study the kinetic, regulatory, and structural mechanisms involved in many of these processes, it would be desirable to be able to alter rapidly the divalent cation concentration with a minimal perturbation in the system being studied. This report describes a photochemical approach to the problem of rapidly increasing free divalent cation concentrations in which brief pulses of light trigger an increase in free [M2+]. The approach we have used is based on our earlier studies demonstrating the utility of a photolabile precursor of ATP, caged ATP, which on photolysis with UV light rapidly released free ATP (6). This work led to the application of the photorelease approach to the study ofthe mechanism ofa wide range of ATP-dependent processes, including the ion-transporting ATPases (7-12) and muscle contraction (13,14), and it has been used for time-resolved structural studies of the sarcoplasmic reticulum Ca2`pump (15) (Fig. 1). Similar principles were used in the present work in which an EDTA molecule, bearing a 2-nitrophenyl moiety on the carbon skeleton, has been synthesized (22), which we anticipated would be photolabile. Our rationale was that the tetraacetic acid molecule (see Fig. 6) with a high affinity for Ca2 + (and/or Mg2 +) ions would photocleave to produce two diacetic acid molecules. Since iminodiacetic acid is known to have a much lower affinity for Ca2 + than does EDTA, the free [Ca2 +] in solution would thus be increased after photocleavage. The present paper describes the properties of such a compound, representative of a series we have synthesized, which fulfills these expectations and promises to be of considerable use in the study of divalent cation-dependent processes. METHODS Synthetic and Analytical. The compound on which this paper focuses was synthesized by reaction of excess iminodiacetic acid diethyl ester with 1-(2-nitro4,5-dimethoxyphenyl)ethane-1,2-diyl 1,2-dibromide (22). The tetraethyl ester product was then hydrolyzed to yield 1- (2-nitro-4,5-dimethoxyphenyl)-N,N,N' ,N'-tetrakis[(oxycarbonyl)

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“…Under these conditions, the sodium pump carries out Na ϩ / Na ϩ exchange where the enzyme shuttles exclusively between E 1 P/E 2 P states of the catalytic cycle. The ratio E 1 P/E 2 P is increased by extracellular Na ϩ , but the effect is opposed if extracellular K ϩ is also present (40,41). Fig.…”

Section: E 1 P/e 2 P Conformational Distribution and Kinetics Of The mentioning

confidence: 93%

Functional Significance of E2 State Stabilization by Specific α/β-Subunit Interactions of Na,K- and H,K-ATPase

Dürr

Tavraz

Dempski

et al. 2009

Journal of Biological Chemistry

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The ␤-subunits of Na,K-ATPase and H,K-ATPase have important functions in maturation and plasma membrane targeting of the catalytic ␣-subunit but also modulate the transport activity of the holoenzymes. In this study, we show that tryptophan replacement of two highly conserved tyrosines in the transmembrane domain of both Na,K-and gastric H,K-ATPase ␤-subunits resulted in considerable shifts of the voltagedependent E 1 P/E 2 P distributions toward the E 1 P state as inferred from presteady-state current and voltage clamp fluorometric measurements of tetramethylrhodamine-6-maleimidelabeled ATPases. The shifts in conformational equilibria were accompanied by significant decreases in the apparent affinities for extracellular K ؉ that were moderate for the Na,K-ATPase ␤-(Y39W,Y43W) mutation but much more pronounced for the corresponding H,K-ATPase ␤-(Y44W,Y48W) variant. Moreover in the Na,K-ATPase ␤-(Y39W,Y43W) mutant, the apparent rate constant for reverse binding of extracellular Na ؉ and the subsequent E 2 P-E 1 P conversion, as determined from transient current kinetics, was significantly accelerated, resulting in enhanced Na ؉ competition for extracellular K ؉ binding especially at extremely negative potentials. Analogously the reverse binding of extracellular protons and subsequent E 2 P-E 1 P conversion was accelerated by the H,K-ATPase ␤-(Y44W,Y48W) mutation, and H ؉ secretion was strongly impaired. Remarkably tryptophan replacements of residues in the M7 segment of Na,K-and H,K-ATPase ␣-subunits, which are at interacting distance to the ␤-tyrosines, resulted in similar E 1 shifts, indicating their participation in stabilization of E 2 . Thus, interactions between selected residues within the transmembrane regions of ␣-and ␤-subunits of P 2C -type ATPases exert an E 2 -stabilizing effect, which is of particular importance for efficient H ؉ pumping by H,K-ATPase under in vivo conditions.

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Sodium pump-mediated ATP:ADP exchange. The sided effects of sodium and potassium ions.

Cited by 42 publications

References 47 publications

Evidence That Ser775 in the α Subunit of the Na,K-ATPase Is a Residue in the Cation Binding Pocket

Evidence That Ser775 in the α Subunit of the Na,K-ATPase Is a Residue in the Cation Binding Pocket

Photolabile chelators for the rapid photorelease of divalent cations.

Functional Significance of E2 State Stabilization by Specific α/β-Subunit Interactions of Na,K- and H,K-ATPase

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