Guanidinium derivatives act as high affinity antagonists of Na+ ions in occlusion sites of Na+,K(+)-ATPase.

David, P.; Mayan, Haim; Cohen, Harry D.; Tal, Daniel M.; Karlish, Steven J. D.

doi:10.1016/s0021-9258(18)48407-4

Cited by 35 publications

(9 citation statements)

References 29 publications

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“…David et al (46) have shown that the bis-guanidine compounds, para-and meta-xylylenebisguanidine (pXBG and mXBG), compete with both Na + and Rb + for occlusion within the enzyme. This inhibition of occlusion was suggested to be from the cytoplasmic surface as the binding of mXBG to the FITC-labeled enzyme produced an "E1" fluorescence signal similar to the binding of Na + , and this signal was reversed by the addition of Rb + (46). An interesting observation by these investigators was that bisguanidine compounds were more potent inhibitors than mono-guanidine compounds (46).…”

Section: Discussionmentioning

confidence: 98%

Similarities and Differences between Organic Cation Inhibition of the Na,K-ATPase and PMCA

et al. 2006

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The effects of three classes of organic cations on the inhibition of the plasma membrane Ca pump (PMCA) were determined and compared to inhibition of the Na pump. Quaternary amines (tetramethylammonium, tetraethylammonium, and tetrapropylammonium, TMA, TEA, and TPA, respectively) did not inhibit PMCA. This is not to imply that PMCA is inherently selective against monovalent cations because guanidine and tetramethylguanidine inhibited PMCA by competing with Ca(2+). The divalent organic cation, ethyl diamine, inhibited PMCA but was not competitive with Ca(2+). In contrast, propyl diamine did compete with Ca(2+) and was about 10-fold more potent than butyl diamine in inhibiting PMCA. For the Na pump, both TEA and TPA inhibited, but TMA did not. TEA, guanidine, and tetramethylguanidine inhibition was competitive with Na(+) for ATPase activation and with K(+) for pNPPase activation, both of which are cytoplasmic substrate cation effects. Thus, these findings are consistent with TEA, guanidine, and tetramethylguanidine inhibiting from the cytoplasmic side of the Na pump; in contrast, we have previously shown that TPA did not inhibit from the cytoplasmic side. The divalent alkane diamines ethyl, propyl, and butyl diamine all inhibited the Na pump and all competed at the intracellular surface. The order of potency was ED > PD > BD consistent with an optimal size for binding; similarly, for the quaternary amines TMA is apparently too small to make appropriate contacts, and TPA is too large. Homology models based upon the high-resolution SERCA structure are included to contextualize the kinetic observations.

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Section: Discussionmentioning

confidence: 98%

Similarities and Differences between Organic Cation Inhibition of the Na,K-ATPase and PMCA

et al. 2006

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“…This phenomenon required much higher concentrations of Br 2 -TITU than for the reversible competitive effects. Although initially it was thought that Br 2 -TITU could act as a lysine-or cysteine-specific modifying reagent, no specific incorporation of 14 C-labeling into the protein was detected using [ 14 C]Br-TITU ( 14 C in the isothiourea moiety) (M. Bar Shimon, D. M. Tal, and S. J. Karlish, unpublished). As we now discuss, the primary effects of Br 2 -TITU on the Ca 2+ -ATPase include some which resemble these additional effects on Na + /K + -ATPase and may provide an explanation.…”

Section: Discussionmentioning

confidence: 99%

“…For example, ethylenediamine is a competitive analogue of monovalent cation binding by the Na + /K + -ATPase, with a dissociation constant of 50 µM (13). More recently, alkyl and aryl bisguanidinium derivatives have been shown to competitively block Na + and K + binding and occlusion (14). On the basis of the structure of amyloride, a widely used K + -sparing diuretic for the treatment of hypertension, Karlish et al (15) have synthesized a number of isothiouronium derivitives, which have so far been found to be the most potent competitive inhibitors with K i values down to 0.32 µM.…”

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confidence: 99%

Interaction of an Aromatic Dibromoisothiouronium Derivative with the Ca²⁺-ATPase of Skeletal Muscle Sarcoplasmic Reticulum

Berman

Karlish

2003

Biochemistry

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Isothiouronium compounds [Hoving, S., Bar-Shimon, M., Tijmes, J. J., Goldshleger, R., Tal, D. M., and Karlish, S. J. (1995) J. Biol. Chem. 270, 29788-29793] act as high-affinity competitive antagonists for Na(+) and K(+) (Rb(+)) on the renal Na(+)/K(+)-ATPase where they favor the E1 conformation. We have now characterized the effects of 1,3-dibromo-2,4,6-tris(methylisothiouronium)benzene (Br(2)-TITU) on the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum. Br(2)-TITU inhibited the Ca(2+)-ATPase, both transport and catalytic activity, with a K(0.5) of 5-15 microM. Maximum inhibition was at 10 min with t(0.5) of 3-5 min. Br(2)-TITU, 100 microM, quenched Trp autofluorescence by 80%, but the residual signal still responded to Ca(2+) binding. Maximum quenching of fluorescence was at pH 9.0. Total E-P levels, during the steady state of turnover of the Ca(2+)-ATPase, were increased from 0.5 to 5.8 nmol x mg(-1) by Br(2)-TITU at pH 6.8. Trinitrophenyl-ATP (TNP-ATP) superfluorescence, which monitors hydrophobicity of the ATP site, was increased 3-4-fold, suggesting that Br(2)-TITU favors an "E2"-like state. Fluorescence was also increased 3-5-fold when E-P was induced with P(i) plus EGTA. Br(2)-TITU increased the rate constants of induction of superfluorescence with ATP plus Ca(2+) from 0.32 to 0.69 s(-1) and with P(i) plus EGTA from 0.84 to 7.45 s(-1). Br(2)-TITU also decreased rate constants for "off" reactions from 2.9 to 0.66 s(-1) and from 10.9 to 0.73 s(-1) for the ATP and P(i) reactions, respectively. Br(2)-TITU, which competitively inhibits the Na(+)/K(+)-ATPase, has a novel effect on the Ca(2+)-ATPase. It promotes accumulation of E2-P species due to increased rate of formation and decreased rate of hydrolysis and quenches tryptophan autofluorescence. Br(2)-TITU could be a useful inhibitor to probe intermediate reactions of the Ca(2+)-ATPase that link catalysis with Ca(2+) translocation.

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“…This is one piece of kinetic evidence in support of an extracellular sodium modifier site (Kropp and Sachs, 1977). Karlish and coworkers (David et al, 1992; have found that guanidinium and related compounds are sodium-like in interactions on the cytoplasmic surface.…”

Section: Introductionmentioning

confidence: 91%

Extracellular Protons Regulate the Extracellular Cation Selectivity of the Sodium Pump

Milanick

Arnett

2002

The Journal of General Physiology

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The effects of 0.3–10 nM extracellular protons (pH 9.5–8.0) on ouabain-sensitive rubidium influx were determined in 4,4′-diisocyanostilbene-2, 2′-disulfonate (DIDS)-treated human and rat erythrocytes. This treatment clamps the intracellular H. We found that rubidium binds much better to the protonated pump than the unprotonated pump; 13-fold better in rat and 34-fold better in human erythrocytes. This clearly shows that protons are not competing with rubidium in this proton concentration range. Bretylium and tetrapropylammonium also bind much better to the protonated pump than the unprotonated pump in human erythrocytes and in this sense they are potassium-like ions. In contrast, guanidinium and sodium bind about equally well to protonated and unprotonated pump in human red cells. In rat red cells, protons actually make sodium bind less well (about sevenfold). Thus, protons have substantially different effects on the binding of rubidium and sodium. The effect of protons on ouabain binding in rat red cells was intermediate between the effects of protons on rubidium binding and on sodium binding. Remarkably, all four cationic inhibitors (bretylium, guanidinium, sodium, and tetrapropylammonium) had similar apparent inhibitory constants for the unprotonated pump (∼5–10 mM). The K d for proton binding to the human pump, with the empty transport site facing extracellularly is 13 nM, whereas the extracellular transport site loaded with sodium is 9.5 nM, and with rubidium is 0.38 nM. In rat red cells there is also a substantial difference in the K d for proton binding to the sodium-loaded pump (14.5 nM) and the rubidium-loaded pump (0.158 nM). These data suggest that important rearrangements occur at the extracellular pump surface as the pump moves between conformations in which the outward facing transport site has sodium bound, is empty, or has rubidium bound and that guanidinium is sodium-like and bretylium and tetrapropylammonium are rubidium-like.

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Guanidinium derivatives act as high affinity antagonists of Na+ ions in occlusion sites of Na+,K(+)-ATPase.

Cited by 35 publications

References 29 publications

Similarities and Differences between Organic Cation Inhibition of the Na,K-ATPase and PMCA

Similarities and Differences between Organic Cation Inhibition of the Na,K-ATPase and PMCA

Interaction of an Aromatic Dibromoisothiouronium Derivative with the Ca²⁺-ATPase of Skeletal Muscle Sarcoplasmic Reticulum

Extracellular Protons Regulate the Extracellular Cation Selectivity of the Sodium Pump

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Guanidinium derivatives act as high affinity antagonists of Na+ ions in occlusion sites of Na+,K(+)-ATPase.

Cited by 35 publications

References 29 publications

Similarities and Differences between Organic Cation Inhibition of the Na,K-ATPase and PMCA

Similarities and Differences between Organic Cation Inhibition of the Na,K-ATPase and PMCA

Interaction of an Aromatic Dibromoisothiouronium Derivative with the Ca2+-ATPase of Skeletal Muscle Sarcoplasmic Reticulum

Extracellular Protons Regulate the Extracellular Cation Selectivity of the Sodium Pump

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Interaction of an Aromatic Dibromoisothiouronium Derivative with the Ca²⁺-ATPase of Skeletal Muscle Sarcoplasmic Reticulum