Effects of cations on the adenosine diphosphate-adenosine triphosphate exchange reaction catalyzed by rat brain microsomes

Wildes, R.A.; Evans, Harold J.; Chiu, Jessie

doi:10.1016/0005-2736(73)90034-5

Cited by 12 publications

(8 citation statements)

References 17 publications

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“…This effect of Na' is clearly a low-affinity phenomenon (and Tris dependent [ Fig . 6]; see also Kuriki and Racker, 1976;Jorgensen and Karlish, 1980 ;Hara and Nakao, 1981 ;Yoda and Yoda, 1982), and it is parallel to a similar low-affinity effect of Na' on ATP:ADP exchange (Wildes et al, 1973;Beauge and Glynn, 1979;Kaplan and Hollis, 1980). Presumably, it is Na' bound to external sites that promotes this phenomenon (Kaplan and Hollis, 1980;Kaplan, 1982), which shows little or no tendency to saturate in the region of 20 to 140-200 mM Na', as with k_B (or k_c) .…”

Section: Discussionmentioning

confidence: 82%

“…With 25 uM ATP and 1 MM Mg2+, this gives maximum phosphorylation, in accordance with the Ko .5 for Na+ for phosphorylation being much lower than 20 mM, since Na' is acting on high-affinity cytoplasmic sites (Blostein, 1979). Similarly, when uncoupled Na' efflux (Sachs, 1970 ;Karlish and Glynn, 1974 ;Blostein, 1979), Na:Na exchange (Garrahan and Glynn, 1967x ;Sachs, 1970 ;Garay and Garrahan, 1973), ATP:ADP exchange (Wildes et al, 1973;Beauge and Glynn, 1979 ;Kaplan and Hollis, 1980 ;Kaplan, 1982), and Na-ATPase activity (Post et al ., 1972;Beauge and Glynn, 1979;Garrahan et al, 1979;Blostein, 1979) are studied, the internal Na' sites have a high affinity for Na+ and in most cases they seem to be saturated at relatively low Na' concentrations . It was therefore not expected that the efflux rate constant, kA, in S2 and Fig.…”

Section: Discussionmentioning

confidence: 99%

“…It is also important for the design of the model in Fig. 8 that the ADP sensitivity of EP is most probably lost at a step preceding the Na:Na exchange reaction since the latter is inhibited by oligomycin, whereas ADP :ATP exchange is stimulated (Garrahan and Glynn, 1967c;Blostein, 1970 ;Wildes et al, 1973), and that the concentration of the ADP-sensitive E, -P is greatly increased by oligomycin (as shown by Hegyvary, 1976, and 1 . Klodos, unpublished data) .…”

Section: A Modelfor Interpreting the Cation Dependence Of Rate Constantsmentioning

confidence: 99%

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Kinetics of Na-ATPase activity by the Na,K pump. Interactions of the phosphorylated intermediates with Na+, Tris+, and K+.

Nørby¹,

Klodos²,

Christiansen³

1983

The Journal of General Physiology

105

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To determine the biochemical events of Na' transport, we studied the interactions of Na', Tris + , and K' with the phosphorylated intermediates of Na,K-ATPase from ox brain . The enzyme was phosphorylated by incubation at 0°C with 1 mM Mg", 25 'LM [ 12 P]ATP, and 20-600 mM Na* with or without Tris + , and the dephosphorylation kinetics of [ 12 P]EP were studied after addition of (1) 1 mM ATP, (2) 2.5 mM ADP, (3) 1 mM ATP plus 20 mM K+, and (4) 2.5 mM ADP plus Na' up to 600 mM. In dephosphorylation types 2-4, the curves were bi-or multiphasic . "ADP-sensitive EP" and "K+-sensitive EP" were determined by extrapolation of the slow phase ofthe curves to the ordinate and their sum was always larger than E,o ., . These results required a minimal model consisting ofthree consecutive EP pools, A, B, and C, where A was ADP sensitive and both B and C were K' sensitive . At high [Na'], B was converted rapidly to A (type 4 experiment). The seven rate coefficients were dependent on [Na''], [Tris+ ], and [K+], and to explain this we developed a comprehensive model for cation interaction with EP . The model has the following features : A, B, and C are equilibrium mixtures of EP forms; EP in A has two to three Na ions bound at high-affinity (internal) sites, pool B has three, and pool C has two to three low-affinity (external) sites . The putative high-affinity outside Na-' site may be on E2 P in pool C. The A -+ B conversion is blocked by K* (and Tris+). We conclude that pool A can be an intermediate only in the Na-ATPase reaction and not in the normal operation of the Na,K pump.

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Section: Discussionmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 99%

Section: A Modelfor Interpreting the Cation Dependence Of Rate Constantsmentioning

confidence: 99%

See 1 more Smart Citation

Kinetics of Na-ATPase activity by the Na,K pump. Interactions of the phosphorylated intermediates with Na+, Tris+, and K+.

Nørby¹,

Klodos²,

Christiansen³

1983

The Journal of General Physiology

105

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“…The conversion of E2P to EP by sodium in very high concentrations (Taniguchi & Post, 1975;Kuriki & Racker, 1976) shows that E2P possesses sodium-binding sites of low affinity. It is, presumably, the conversion of E2P to E1P promoted by the occupation of these sites by sodium ions that allows sodium in high concentrations to stimulate ATP-ADP exchange (Wildes, Evans & Chiu, 1973;Beauge6 & Glynn, 1979). But the stimulation of ATP-ADP exchange by sodium ions at high concentrations is known to be an effect of extracellular sodium.…”

Section: Discussionmentioning

confidence: 99%

The occlusion of sodium ions within the mammalian sodium‐potassium pump: its role in sodium transport.

Glynn¹,

Hara²,

Richards³

1984

The Journal of Physiology

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The hypothesis that the ADP-sensitive form of phosphorylated Na+, K+-ATPase contains occluded sodium ions has been tested by a procedure which involves (i) modifying the enzyme with alpha-chymotrypsin or N-ethylmaleimide (NEM) so that the ADP-sensitive form is more stable than it is in the native enzyme, (ii) phosphorylating the modified enzyme with ATP in the presence of labelled sodium ions, and (iii) forcing the phosphorylated enzyme rapidly through a cation-exchange column and measuring the labelled sodium in the effluent. The results show that ADP-sensitive phosphoenzyme prepared from alpha-chymotrypsin- or NEM-modified Na+, K+-ATPase is able to carry labelled sodium ions through a cation-exchange resin. This behaviour was not seen with native Na+, K+-ATPase or when phosphorylation was prevented by the omission of magnesium ions or by the substitution of adenylyl(beta, gamma-methylene)diphosphonate (AMP-PCP) for ATP. The occluded sodium ions were rapidly released when the phosphoenzyme was dephosphorylated by ADP. When alpha-chymotrypsin-modified enzyme was phosphorylated by ATP with 1 mM-sodium in the medium, close to three sodium ions were occluded per phospho group. The stoicheiometry at much lower sodium concentrations could not be determined satisfactorily. A consideration of the rate constants of the reactions thought to be involved in the occlusion of sodium and in the release of sodium from the occluded state shows that, so far as they are known, these constants are compatible with the hypothesis that the occluded-sodium form of the phosphoenzyme plays a central role in sodium transport through the pump.

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“…This set of observations supports the suggestion that Na:Na exchange transport is accompanied by the ATP:ADP exchange reaction (Glynn and Hoffman, 1971), first observed in partially purified Na,K-ATPase preparations by Fahn et al (1966). Subsequent work has shown that the rate of ATP:ADP exchange shows a complex dependence upon Na ion concentration with enzyme isolated from a variety of sources (Wildes et al, 1973;Beauge and Glynn, 1979;Kaplan and Hollis, 1980;Kaplan et al, 1981).…”

Section: Introductionmentioning

confidence: 99%

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

Kaplan¹

1982

The Journal of General Physiology

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A B S T R A C T Resealed human red cell ghosts containing caged ATP (Kaplan et al., 1978) and [SH]ADP were irradiated at 340 nm. The photochemical release of free ATP initiated a rapid transphosphorylation reaction (ATP:ADP exchange), a component of which is inhibited by ouabain. The reaction rate was measured by following the rate of appearance of [aH]ATP. The sodium pumpmediated ATP:ADP exchange reaction showed high-affinity stimulation by Mg ions (<10/.tM) and was inhibited at higher levels. At optimal [Mg], extracellular Na (Nao) had a biphasic effect. Nao progressively inhibited the reaction rate between 0 and 10 mM and stimulated at higher levels. Intracellular Na (Nai) activated the reaction; the rate was maximal when Nai was 1 mM and remained unaltered up to 115 mM Nai at constant Nao. ExtraeeUular K ions (Ko) inhibited the reaction; at high Nao, half-maximal inhibition was observed with 0.9 mM Ko. Lio inhibited the exchange rate with a lower affinity than Ko; halfmaximal inhibition was produced by ~50 mM Lio. Intracellular K ions were without dramatic effect on the reaction rate in the concentration range where Ko inhibited completely. The relationship between these observations and previous studies on porous preparations is discussed, as well as the extent to which these observations support the hypothesis that the sodium pump-mediated ATP:ADP exchange reaction accompanies the Na:Na exchange transport mode of the sodium pump.

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Effects of cations on the adenosine diphosphate-adenosine triphosphate exchange reaction catalyzed by rat brain microsomes

Cited by 12 publications

References 17 publications

Kinetics of Na-ATPase activity by the Na,K pump. Interactions of the phosphorylated intermediates with Na+, Tris+, and K+.

Kinetics of Na-ATPase activity by the Na,K pump. Interactions of the phosphorylated intermediates with Na+, Tris+, and K+.

The occlusion of sodium ions within the mammalian sodium‐potassium pump: its role in sodium transport.

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

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