scholarly journals The Arabidopsis thaliana K+-Uptake Permease 5 (AtKUP5) Contains a Functional Cytosolic Adenylate Cyclase Essential for K+ Transport

2018 ◽  
Vol 9 ◽  
Author(s):  
Inas Al-Younis ◽  
Aloysius Wong ◽  
Fouad Lemtiri-Chlieh ◽  
Sandra Schmöckel ◽  
Mark Tester ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Adenylate Cyclase ◽  
K Uptake ◽  
K Transport

scholarly journals The Arabidopsis thaliana K+ -uptake permease 7 (AtKUP7) contains a functional cytosolic adenylate cyclase catalytic centre

FEBS Letters ◽  
2015 ◽  
Vol 589 (24PartB) ◽  
pp. 3848-3852 ◽  
Author(s):  
Inas Al-Younis ◽  
Aloysius Wong ◽  
Chris Gehring
Keyword(s):  
Arabidopsis Thaliana ◽  
Adenylate Cyclase ◽  
K Uptake

scholarly journals The Effect of AtHKT1;1 or AtSOS1 Mutation on the Expressions of Na+ or K+ Transporter Genes and Ion Homeostasis in Arabidopsis thaliana under Salt Stress

2019 ◽  
Vol 20 (5) ◽  
pp. 1085 ◽  
Author(s):  
Qian Wang ◽  
Chao Guan ◽  
Pei Wang ◽  
Qing Ma ◽  
Ai-Ke Bao ◽  
...  
Keyword(s):  
Arabidopsis Thaliana ◽  
Salt Stress ◽  
Plant Growth ◽  
Expression Profiles ◽  
Ion Homeostasis ◽  
Wild Type ◽  
Na Transport ◽  
K Uptake ◽  
Selective Transport ◽  
K Transport

HKT1 and SOS1 are two key Na+ transporters that modulate salt tolerance in plants. Although much is known about the respective functions of HKT1 and SOS1 under salt conditions, few studies have examined the effects of HKT1 and SOS1 mutations on the expression of other important Na+ and K+ transporter genes. This study investigated the physiological parameters and expression profiles of AtHKT1;1, AtSOS1, AtHAK5, AtAKT1, AtSKOR, AtNHX1, and AtAVP1 in wild-type (WT) and athkt1;1 and atsos1 mutants of Arabidopsis thaliana under 25 mM NaCl. We found that AtSOS1 mutation induced a significant decrease in transcripts of AtHKT1;1 (by 56–62% at 6–24 h), AtSKOR (by 36–78% at 6–24 h), and AtAKT1 (by 31–53% at 6–24 h) in the roots compared with WT. This led to an increase in Na+ accumulation in the roots, a decrease in K+ uptake and transportation, and finally resulted in suppression of plant growth. AtHKT1;1 loss induced a 39–76% (6–24 h) decrease and a 27–32% (6–24 h) increase in transcripts of AtSKOR and AtHAK5, respectively, in the roots compared with WT. At the same time, 25 mM NaCl decreased the net selective transport capacity for K+ over Na+ by 92% in the athkt1;1 roots compared with the WT roots. Consequently, Na+ was loaded into the xylem and delivered to the shoots, whereas K+ transport was restricted. The results indicate that AtHKT1;1 and AtSOS1 not only mediate Na+ transport but also control ion uptake and the spatial distribution of Na+ and K+ by cooperatively regulating the expression levels of relevant Na+ and K+ transporter genes, ultimately regulating plant growth under salt stress.

scholarly journals CATION TRANSPORT IN YEAST

1956 ◽  
Vol 39 (5) ◽  
pp. 687-704 ◽  
Author(s):  
Ernest C. Foulkes
Keyword(s):  
Cell Membrane ◽  
Dissociation Constant ◽  
Concentration Gradient ◽  
Cation Transport ◽  
K Uptake ◽  
Present Evidence ◽  
Inhibitor Complex ◽  
Maximum Value ◽  
Low Concentrations ◽  
K Transport

1. The distribution of azide added to suspensions of bakers' yeast was studied under various conditions. The recovery of azide was estimated in the volume of water into which low concentrations of electrolytes can readily diffuse (anion space). Considerable azide disappeared from this anion space. 2. The incomplete recovery of azide in the anion space is due to its uptake by the cells. This uptake occurs against a concentration gradient at 0°C., and is attributed to binding of azide by cell constituents. 3. Confirmatory evidence is presented that one such constituent is the K carrier in the cell membrane. The azide inhibition of K transport is not mediated by inhibition of cytochrome oxidase in the mitochondria. 4. From the amount of combined azide and the experimentally determined dissociation constant of the K carrier-inhibitor complex, the maximum value for the concentration of this carrier is calculated as 0.1 µM/gm. yeast. 5. The addition of glucose and PO4 causes a secondary K uptake which is not azide-sensitive and is clearly distinct from the primary, azide-sensitive mechanism. 6. The existence of a separate carrier responsible for Na extrusion is reconsidered. It is concluded that present evidence does not necessitate the assumption that such a carrier is active in yeast.

scholarly journals Influx and accumulation of Cs+ by the akt1 mutant of Arabidopsis thaliana (L.) Heynh. lacking a dominant K+ transport system

2001 ◽  
Vol 52 (357) ◽  
pp. 839-844 ◽  
Author(s):  
Martin R. Broadley ◽  
Abraham J. Escobar‐Gutiérrez ◽  
Helen C. Bowen ◽  
Neil J. Willey ◽  
Philip J. White
Keyword(s):  
Arabidopsis Thaliana ◽  
Transport System ◽  
K Transport

Cell volume regulation by skate erythrocytes: role of potassium

1990 ◽  
Vol 258 (5) ◽  
pp. R1217-R1223 ◽  
Author(s):  
K. G. Dickman ◽  
L. Goldstein
Keyword(s):  
Cell Volume ◽  
Phorbol Ester ◽  
Volume Regulation ◽  
Regulatory Volume Decrease ◽  
Cell Volume Regulation ◽  
Disulfonic Acid ◽  
Ionophore A23187 ◽  
K Uptake ◽  
K Transport

The role of K transport during cell volume regulation in response to extracellular osmolality, protein kinase C activation, and cellular Ca was examined in skate (Raja erinacea) red blood cells (RBC). Reduction of medium osmolality from 960 to 660 mosmol/kgH2O had no effect on K uptake or efflux despite a 25% increase in cell volume. Further reduction to 460 mosmol/kgH2O caused K uptake to double and K efflux to triple resulting in net K loss. Net K efflux in 460 mosmol/kgH2O medium was correlated with the presence of a regulatory volume decrease, which was sensitive to the anion transport inhibitor 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and insensitive to chloride replacement. K-K exchange was absent in both isotonic and hypotonic media. Treatment with the Ca ionophore A23187 in the presence of Ca had no effect on either cell volume or K efflux in isotonic medium, indicating the absence of Ca-activated K transport. In contrast, phorbol ester treatment caused cell volume, Na content, and proton and K efflux to increase. Consistent with activation of Na-H exchange, phorbol ester effects were inhibited by dimethylamiloride. This study constitutes the first demonstration of volume-sensitive K transport in RBC from the most primitive vertebrate studied to date.

scholarly journals Cation transport in Escherichia coli. IX. Regulation of K transport.

1978 ◽  
Vol 72 (3) ◽  
pp. 283-295 ◽  
Author(s):  
D B Rhoads ◽  
W Epstein
Keyword(s):  
Escherichia Coli ◽  
Steady State ◽  
Cation Transport ◽  
Transport Systems ◽  
Energy Requirements ◽  
Protonmotive Force ◽  
K Uptake ◽  
Kinetics Of ◽  
K Transport ◽  
External K

Kinetics of K exchange in the steady state and of net K uptake after osmotic upshock are reported for the four K transport systems of Escherichia coli: Kdp, TrkA, TrkD, and TrkF. Energy requirements for K exchange are reported for the Kdp and TrkA systems. For each system, kinetics of these two modes of K transport differ from those for net K uptake by K-depleted cells (Rhoads, D. B. F.B. Walters, and W. Epstein. 1976. J. Gen. Physiol. 67:325-341). The TrkA and TrkD systems are inhibited by high intracellular K, the TrkF system is stimulated by intracellular K, whereas the Kdp system is inhibited by external K when intracellular K is high. All four systems mediate net K uptake in response to osmotic upshock. Exchange by the Kdp and TrkA systems requires ATP but is not dependent on the protonmotive force. Energy requirements for the Kdp system are thus identical whether measured as net K uptake or K exchange, whereas the TrkA system differs in that it is dependent on the protonmotive force only for net K uptake. We suggest that in both the Kpd and TrkA systems formation of a phosphorylated intermediate is necessary for all K transport, although exchange transport may not consume energy. The protonmotive-force dependence of the TrkA system is interpreted as a regulatory influence, limiting this system to exchange except when the protonmotive force is high.

scholarly journals Influence of Haemoglobin Conformation, Nitrite and Eicosanoids on K+ Transport Across the Carp Red Blood Cell Membrane

1992 ◽  
Vol 171 (1) ◽  
pp. 349-371 ◽  
Author(s):  
FRANK B. JENSEN
Keyword(s):  
Membrane Potential ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Quaternary Structure ◽  
Large Fraction ◽  
Nordihydroguaiaretic Acid ◽  
K Uptake ◽  
Root Effect ◽  
T State ◽  
K Transport

The regulation of K+ transport across the red blood cell (RBC) membrane by haemoglobin (Hb) conformation was studied in carp, and the K+ transport mechanisms were identified. When a large proportion of Hb in the R quaternary structure was secured by oxygenation of blood at pH8.14, a net RBC K+ efflux was induced, which was accompanied by RBC shrinkage. This K+ efflux was resistant to ouabain and inhibited by furosemide and DIDS and by substitution of NO3− for Cl−, showing it to result from a K+/Cl− cotransport mechanism. Deoxygenation of the RBCs (Hb in T structure) eliminated the Cl−-dependent K+ efflux and resulted in a net K+ uptake via the Na+/K+ pump. These changes were fully reversible. Nitrite-induced methaemoglobin formation in deoxygenated blood, which converts a large fraction of the T structure Hb into an R-like conformation, shifted the K+ uptake to a Cl−-dependent K+ efflux similar to that seen in oxygenated cells. When the allosteric equilibrium between the R and T structures of Hb was gradually shifted towards the T state by decreases in pH, the Cl−-dependent K+ efflux from oxygenated cells decreased. At pH7.52, where the Root effect caused a potent stabilisation of the T state, the K+ efflux was reversed to a net K+ uptake. A similar change was induced in methaemoglobin-containing deoxygenated blood, since low pH also favours a T-like conformation of metHb. The variable K+ fluxes could not be related to changes in membrane potential or pH but were always directly related to the experimental modulation of the relative proportions of R- and T-structure Hb. It is proposed that Hb conformation governs K+ movements via a different binding of T and R structures to integral membrane proteins, and that a large fraction of R-structure Hb triggers the Cl−dependent K+ efflux mechanism. Application of inhibitors and a substrate of prostaglandin and leukotriene synthesis did not influence the K+ efflux from oxygenated erythrocytes. However, a fraction of the K+ efflux from nitrite-treated deoxygenated cells was inhibited by nordihydroguaiaretic acid, suggesting that a slightly larger K+ efflux from these RBCs than from oxygenated RBCs was related to leukotriene production caused by nitrite entry. A much larger influx of nitrite to deoxygenated than to oxygenated RBCs was positively correlated with the distribution ratio of H+ and the membrane potential, supporting the view that nitrite primarily enters the cells via conductive transport. The physiological implications of the results are discussed.

scholarly journals Volume-sensitive K transport in human erythrocytes.

1986 ◽  
Vol 88 (6) ◽  
pp. 719-738 ◽  
Author(s):  
D Kaji
Keyword(s):  
Cell Volume ◽  
Human Erythrocytes ◽  
Cell Swelling ◽  
K Channel ◽  
K Uptake ◽  
Transport Pathway ◽  
Free Media ◽  
K Transport ◽  
Hypotonic Swelling ◽  
External K

Studies have been carried out on human erythrocytes to examine the alterations of K transport induced by swelling or shrinking the cells by osmotic and isosmotic methods. Hypotonic swelling of erythrocytes (relative cell volume, 1.20) resulted in a striking, four- to fivefold augmentation in the ouabain-resistant K influx over the value obtained at a normal cell volume. Shrinking the cells in hypertonic media resulted in a small but statistically significant reduction in K influx. Three different methods of varying cell volume gave similar results. These include the addition of sucrose and of NaCl to hypotonic media and the isosmotic (nystatin) method. The major fraction of the K influx in swollen cells is specific in its requirement for Cl or Br and is not supported by thiocyanate, iodide, nitrate, methylsulfate, or acetate. Bumetanide (0.1 mM), MK-196 (0.2 mM), and piretanide (1 mM) are poorly effective in suppressing K uptake in swollen cells, but at higher concentrations, bumetanide (1 mM) inhibits 80% of the Cl-dependent K influx in swollen cells. The bumetanide concentration required to inhibit 50% of the Cl-dependent K influx is 0.17 mM. The volume-sensitive K influx is independent of both extracellular and intracellular Na, so that the (Na + K + 2Cl) cotransport pathway is not a likely mediator of the volume-sensitive K transport. A variety of inhibitors of the Ca-activated K channel are ineffective in suppressing swelling-induced K influx. Like K uptake, the efflux of K is also enhanced by cell swelling. Swelling-activated K efflux is Cl dependent, is independent of extracellular and intracellular Na, and is observed with both hypotonic and isosmotic methods of cell swelling. The activation of K efflux by cell swelling is observed in K-free media, which suggests that the volume-sensitive K transport pathway is capable of net K efflux. The addition of external K to hypotonic media resulted in an increase in K efflux compared with the efflux in K-free media, and this increase was probably due to K/K exchange. Thus, hypotonic or isosmotic swelling of human erythrocytes results in the activation of a ouabain-resistant, Cl-dependent, Na-independent transport pathway that is capable of mediating both net K efflux and K/K exchange.

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