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Gene Review

KAT1  -  potassium channel KAT1

Arabidopsis thaliana

Synonyms: MPL12.2, MPL12_2, potassium channel in Arabidopsis thaliana 1
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Disease relevance of KAT1


High impact information on KAT1

  • This report shows that a single messenger RNA transcript from the Arabidopsis thaliana KAT1 complementary DNA confers the functional expression of a hyperpolarization-activated K+ channel in Xenopus oocytes [3].
  • These functional characteristics, typical of inward-rectifying K+ channels in eukaryotic cells, demonstrate that KAT1 encodes an inward-rectifying K+ channel [3].
  • The channels encoded by KAT1 are highly selective for K+ over other monovalent cations, are blocked by tetraethylammonium and barium, and have a single channel conductance of 28 +/- 7 picosiemens with 118 millimolar K+ in the bathing solution [3].
  • Selective mobility and sensitivity to SNAREs is exhibited by the Arabidopsis KAT1 K+ channel at the plasma membrane [4].
  • Thus, KAB1 was determined to be expressed in plant organs (leaves) and cell types (guard cells) that are sites of KAT1 expression in the plant [5].

Chemical compound and disease context of KAT1

  • The infection of Sf9 cells with KAT1-recombinant baculovirus resulted in functional expression of KAT1 channels, which was monitored by inward-rectifying, K+-selective (impermeable to Na+ and even NH4+) ionic conductance in whole-cell patch-clamp recordings [6].

Biological context of KAT1

  • The KAT1 cDNA contains an open reading frame capable of encoding a 78-kDa protein that shares structural features found in the Shaker superfamily of K+ channels [7].
  • KAT1 was cloned by its ability to suppress a K+ transport-defective phenotype in mutant Saccharomyces cerevisiae cells [7].
  • In control experiments, the inactive point mutation in KAT1, T256R, did not complement for K+ uptake in E. coli [1].
  • Unlike the plant inward-rectifying guard cell K+ channels KAT1 and KST1, the AKT3 channels were only weakly regulated by the membrane potential [8].
  • Despite the additional 14 amino acids in H5, this motif in KAT1 is also involved in the formation of the ion-conducting pore because amino acid substitutions at Leu-251, Thr-256, Thr-259, and Thr-260 resulted in functional channels with modified ionic selectivity and inhibition [9].

Anatomical context of KAT1

  • These data provide direct evidence that KAT1 functions as a plasma membrane K+ channel in vivo and that K+in channels constitute an important mechanism for light-induced stomatal opening [10].
  • To test whether the guard cell K(+) channel KAT1 is essential for stomatal opening, a knockout mutant, KAT1En-1, was isolated from an En-1 mutagenized Arabidopsis thaliana population [11].
  • Microscopic observation after immunogold staining revealed that the expressed AKT1 and KAT1 polypeptides were mainly associated with internal membranes, but that a minute fraction was targeted to the cell membrane [2].
  • Thus, this change in the electrical properties of the K+-uptake channel in hypocotyl protoplasts resulted from an auxin-induced increase of active KAT1 proteins [12].
  • In this study, we used in vitro translation and translocation experiments to evaluate interactions between residues in the voltage sensor of a hyperpolarization-activated potassium channel, KAT1, and their effect on the final topology in the endoplasmic reticulum (ER) membrane [13].

Associations of KAT1 with chemical compounds

  • The 115 region between Pro-247 and Pro-271 in KAT1 contains 14 additional amino acids when compared with Shaker [Aldrich, R. W. (1993) Nature (London) 362, 107-108] [9].
  • These single site mutations gave rise to Rb+- and NH4(+)-selective channels with Rb+ and NH4+ currents that were approximately 10-13-fold greater in amplitude than K+ currents, whereas the NH4+ to K+ current amplitude ratio of wild type KAT1 was 0.28 [14].
  • Although this histidine is highly conserved among all plant K+ uptake channels cloned so far, the pH-dependent gating of the Arabidopsis thaliana guard cell K+ channel KAT1 was not affected by mutations of this histidine [15].
  • From our electrophysiological studies on channel mutants with respect to the pore histidine as well as the aspartate, we conclude that the common proton-supported shift in the voltage dependence of KST1 and KAT1 is based on distinct molecular elements [15].
  • In KAT1-knockout mutants, K+ currents after auxin stimulation were characterised by reduced amplitudes [12].

Other interactions of KAT1

  • Here we report the isolation of a novel Arabidopsis thaliana cDNA (AKT2) that is highly homologous to the two previously identified K+ channel genes, KAT1 and AKT1 [16].
  • Tests with deletion mutants demonstrate that the C terminus of KAT1 and AKT1 is necessary for physical assembly of complexes [17].
  • More than KAT1, KAT2 displays functional features resembling those of native inward K(+) channels in guard cells [18].
  • Although we used primers for all members of the Shaker K+ channel family, we identified only AKT2, KAT1 and KCO6 transcripts [19].
  • In this study, we provide experimental evidence that the KAB1 polypeptide forms a tight physical association with the Arabidopsis K+ channel alpha subunit, KAT1 [5].

Analytical, diagnostic and therapeutic context of KAT1

  • In the present study, we utilized a combination of random site-directed mutagenesis, genetic screening in a potassium uptake-deficient yeast strain, and electrophysiological analysis in Xenopus oocytes to identify strong modifications in cation selectivity of the inward rectifying K+ channel KAT1 [14].
  • Increasing KAT1 expression in Xenopus oocytes by polyadenylation of the KAT1 mRNA increased the current amplitude and led to higher levels of KAT1 protein, as assayed in western blots [16].
  • Molecular dissection of the contribution of negatively and positively charged residues in S2, S3, and S4 to the final membrane topology of the voltage sensor in the K+ channel, KAT1 [13].
  • Immunofluorescence with an antibody against the flag epitope and an anti-C terminal KAT1 determined the membrane localization of these epitopes and the orientation of the KAT1 channel in the membrane [20].


  1. Determination of transmembrane topology of an inward-rectifying potassium channel from Arabidopsis thaliana based on functional expression in Escherichia coli. Uozumi, N., Nakamura, T., Schroeder, J.I., Muto, S. Proc. Natl. Acad. Sci. U.S.A. (1998) [Pubmed]
  2. The baculovirus/insect cell system as an alternative to Xenopus oocytes. First characterization of the AKT1 K+ channel from Arabidopsis thaliana. Gaymard, F., Cerutti, M., Horeau, C., Lemaillet, G., Urbach, S., Ravallec, M., Devauchelle, G., Sentenac, H., Thibaud, J.B. J. Biol. Chem. (1996) [Pubmed]
  3. Expression of an inward-rectifying potassium channel by the Arabidopsis KAT1 cDNA. Schachtman, D.P., Schroeder, J.I., Lucas, W.J., Anderson, J.A., Gaber, R.F. Science (1992) [Pubmed]
  4. Selective mobility and sensitivity to SNAREs is exhibited by the Arabidopsis KAT1 K+ channel at the plasma membrane. Sutter, J.U., Campanoni, P., Tyrrell, M., Blatt, M.R. Plant Cell (2006) [Pubmed]
  5. Physical association of KAB1 with plant K+ channel alpha subunits. Tang, H., Vasconcelos, A.C., Berkowitz, G.A. Plant Cell (1996) [Pubmed]
  6. Functional expression of the plant K+ channel KAT1 in insect cells. Marten, I., Gaymard, F., Lemaillet, G., Thibaud, J.B., Sentenac, H., Hedrich, R. FEBS Lett. (1996) [Pubmed]
  7. Functional expression of a probable Arabidopsis thaliana potassium channel in Saccharomyces cerevisiae. Anderson, J.A., Huprikar, S.S., Kochian, L.V., Lucas, W.J., Gaber, R.F. Proc. Natl. Acad. Sci. U.S.A. (1992) [Pubmed]
  8. AKT3, a phloem-localized K+ channel, is blocked by protons. Marten, I., Hoth, S., Deeken, R., Ache, P., Ketchum, K.A., Hoshi, T., Hedrich, R. Proc. Natl. Acad. Sci. U.S.A. (1999) [Pubmed]
  9. Changes in voltage activation, Cs+ sensitivity, and ion permeability in H5 mutants of the plant K+ channel KAT1. Becker, D., Dreyer, I., Hoth, S., Reid, J.D., Busch, H., Lehnen, M., Palme, K., Hedrich, R. Proc. Natl. Acad. Sci. U.S.A. (1996) [Pubmed]
  10. Expression of a Cs(+)-resistant guard cell K+ channel confers Cs(+)-resistant, light-induced stomatal opening in transgenic arabidopsis. Ichida, A.M., Pei, Z.M., Baizabal-Aguirre, V.M., Turner, K.J., Schroeder, J.I. Plant Cell (1997) [Pubmed]
  11. KAT1 is not essential for stomatal opening. Szyroki, A., Ivashikina, N., Dietrich, P., Roelfsema, M.R., Ache, P., Reintanz, B., Deeken, R., Godde, M., Felle, H., Steinmeyer, R., Palme, K., Hedrich, R. Proc. Natl. Acad. Sci. U.S.A. (2001) [Pubmed]
  12. Auxin activates KAT1 and KAT2, two K+-channel genes expressed in seedlings of Arabidopsis thaliana. Philippar, K., Ivashikina, N., Ache, P., Christian, M., Lüthen, H., Palme, K., Hedrich, R. Plant J. (2004) [Pubmed]
  13. Molecular dissection of the contribution of negatively and positively charged residues in S2, S3, and S4 to the final membrane topology of the voltage sensor in the K+ channel, KAT1. Sato, Y., Sakaguchi, M., Goshima, S., Nakamura, T., Uozumi, N. J. Biol. Chem. (2003) [Pubmed]
  14. Identification of strong modifications in cation selectivity in an Arabidopsis inward rectifying potassium channel by mutant selection in yeast. Uozumi, N., Gassmann, W., Cao, Y., Schroeder, J.I. J. Biol. Chem. (1995) [Pubmed]
  15. Distinct molecular bases for pH sensitivity of the guard cell K+ channels KST1 and KAT1. Hoth, S., Hedrich, R. J. Biol. Chem. (1999) [Pubmed]
  16. Multiple genes, tissue specificity, and expression-dependent modulationcontribute to the functional diversity of potassium channels in Arabidopsis thaliana. Cao, Y., Ward, J.M., Kelly, W.B., Ichida, A.M., Gaber, R.F., Anderson, J.A., Uozumi, N., Schroeder, J.I., Crawford, N.M. Plant Physiol. (1995) [Pubmed]
  17. K+ channel interactions detected by a genetic system optimized for systematic studies of membrane protein interactions. Obrdlik, P., El-Bakkoury, M., Hamacher, T., Cappellaro, C., Vilarino, C., Fleischer, C., Ellerbrok, H., Kamuzinzi, R., Ledent, V., Blaudez, D., Sanders, D., Revuelta, J.L., Boles, E., André, B., Frommer, W.B. Proc. Natl. Acad. Sci. U.S.A. (2004) [Pubmed]
  18. Guard cell inward K+ channel activity in arabidopsis involves expression of the twin channel subunits KAT1 and KAT2. Pilot, G., Lacombe, B., Gaymard, F., Cherel, I., Boucherez, J., Thibaud, J.B., Sentenac, H. J. Biol. Chem. (2001) [Pubmed]
  19. Isolation of AtSUC2 promoter-GFP-marked companion cells for patch-clamp studies and expression profiling. Ivashikina, N., Deeken, R., Ache, P., Kranz, E., Pommerrenig, B., Sauer, N., Hedrich, R. Plant J. (2003) [Pubmed]
  20. Orientation of Arabidopsis thaliana KAT1 channel in the plasma membrane. Mura, C.V., Cosmelli, D., Muñoz, F., Delgado, R. J. Membr. Biol. (2004) [Pubmed]
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