Chapter 2 : The Ktn Domain and Its Role as a Channel and Transporter Regulator

MyBook is a cheap paperback edition of the original book and will be sold at uniform, low price.

Preview this chapter:
Zoom in

The Ktn Domain and Its Role as a Channel and Transporter Regulator, Page 1 of 2

| /docserver/preview/fulltext/10.1128/9781555816452/9781555813284_Chap02-1.gif /docserver/preview/fulltext/10.1128/9781555816452/9781555813284_Chap02-2.gif


In this chapter, the author describes the Ktn domain and its role as a channel and transporter regulator, briefly considers the other bacterial systems that possess Ktn and Ktn-related domains, and, finally presents a more detailed analysis of one's understanding of the structure and operation of the KefC system. The domain can be found as an integral part of the main channel-forming protein (e.g., MthK, Kch, and KefC) as an ancillary extrinsic membrane protein (KtrA, TrkA) and as a protein attached to the membrane by a single transmembrane span (AmhM in ). The protein is one of the shortest members of the family at 434 residues, truncation of the carboxy-terminal domain being responsible for the shorter length and leading to loss of the Ktn domain. Potassium uptake systems in bacteria essentially fall into three categories: K-transporting primary ATPases, such as Kdp; secondary transporters, such as Kup; and more complex systems, e.g., TrkAEH in and KtrAB in . The cation-proton antiports 2 (CPA2) family of proteins was originally defined around the monovalent cation-proton antiports but is now thought to contain channels as well as transporters. The analysis of the crystal structures of K channels has generated great insights into the mechanism of ion selectivity. It seems almost certain that the analysis of the biochemistry of channels such as MthK and KirBac will provide new insights into the gating mechanism.

Citation: Booth I, Edwards M, Gunasekera B, Li C, Miller S. 2005. The Ktn Domain and Its Role as a Channel and Transporter Regulator, p 21-40. In Kubalski A, Martinac B (ed), Bacterial Ion Channels and Their Eukaryotic Homologs. ASM Press, Washington, DC. doi: 10.1128/9781555816452.ch2

Key Concept Ranking

Bacterial Proteins
Bacteria and Archaea
Peripheral Membrane Proteins
Integral Membrane Proteins
Highlighted Text: Show | Hide
Loading full text...

Full text loading...


Image of Figure 1
Figure 1

The organization of Ktn-bearing channels and transporters. The structures are shown schematically, with the sizes of the domains approximately to scale according to the numbers of amino acids. Key: dark gray, membrane domain; black, Ktn domain; white or shaded, SAM domains; black line, linker that covalently attaches Ktn to the membrane domain. Note that TrkA has two covalently linked Ktn and SAM domains. The numbers 1 and 2 refer to the first and second domains throughout (see text for details).

Citation: Booth I, Edwards M, Gunasekera B, Li C, Miller S. 2005. The Ktn Domain and Its Role as a Channel and Transporter Regulator, p 21-40. In Kubalski A, Martinac B (ed), Bacterial Ion Channels and Their Eukaryotic Homologs. ASM Press, Washington, DC. doi: 10.1128/9781555816452.ch2
Permissions and Reprints Request Permissions
Download as Powerpoint
Image of Figure 2
Figure 2

Structure and mutations in KefC. The figure depicts the hydrophobicity of KefC ( ) and the locations of the different structural features. The positions of mutations that alter the gating of the KefC channel are indicated ( ; unpublished data). Residues indicated above the Ktn and SAM domains inhibit KefC function when mutated and those below the domain increase spontaneous activity. For the linker the single diminished function mutation is shown in brackets. The conserved sequence between helices 8 and 9 is SEYRHALESDIEP, which extends beyond the core HALESDIEP sequence that has been analyzed previously ( ). Arrows indicate the three critical acidic residues that when mutated alter KefC and KefB activity. The position of the putative voltage sensor is indicated (Rxxx).

Citation: Booth I, Edwards M, Gunasekera B, Li C, Miller S. 2005. The Ktn Domain and Its Role as a Channel and Transporter Regulator, p 21-40. In Kubalski A, Martinac B (ed), Bacterial Ion Channels and Their Eukaryotic Homologs. ASM Press, Washington, DC. doi: 10.1128/9781555816452.ch2
Permissions and Reprints Request Permissions
Download as Powerpoint


1. Accardi, A.,, L. Kolmakova-Partensky,, C. Williams,, and C. Miller. 2004. Ionic currents mediated by a prokaryotic homologue of CLC Cl- channels. J. Gen. Physiol. 123:109119.
2. Altendorf, K.,, and W. Epstein. 1994. Kdp-Atpase of Escherichia coli. Cell. Physiol. Biochem. 4:160168.
3. Altendorf, K.,, M. Gassel,, W. Puppe,, T. Mollenkamp,, A. Zeeck,, C. Boddien,, K. Fendler,, E. Bamberg,, and S. Drose. 1998. Structure and function of the Kdp-ATPase of Escherichia coli. Acta Physiol. Scand. 163:137146.
4. Bakker, E. P.,, I. R. Booth,, U. Dinnbier,, W. Epstein,, and A. Gajewska. 1987. Evidence for multiple K+ export systems in Escherichia coli. J. Bacteriol. 169:37433749.
5. Bakker, E. P.,, and W. E. Mangerich. 1982. N-ethylmaleimide induces K+-H+ antiport activity in Escherichia coli K-12. FEBS Lett. 140:177180.
6. Bass, R. B.,, P. Strop,, M. Barclay,, and D. C. Rees. 2002. Crystal structure of Escherichia coli MscS, a voltage-modulated and mechanosensitive channel. Science 298:15821587.
7. Bengoechea, J. A.,, and M. Skurnik. 2000. Temperature-regulated efflux pump/potassium antiporter system mediates resistance to cationic antimicrobial peptides in Yersinia. Mol. Microbiol. 37:6780.
8. Biggin, P. C.,, T. Roosild,, and S. Choe. 2000. Potassium channel structure: domain by domain. Curr. Opin. Struct. Biol. 10:456461.
9. Booth, I. R., 2003. Bacterial ion channels, p. 91112. In J. K. Setlow (ed.), Genetic Engineering: Principles and Methods, vol. 25. Kluwer Academic/Plenum Publishers, New York, N.Y.
10. Bossemeyer, D.,, A. Borchard,, D. C. Dosch,, G. C. Helmer,, W. Epstein,, I. R. Booth,, and E. P. Bakker. 1989a. K+ transport protein TrkA of Escherichia coli is a peripheral membrane protein that requires other trk gene products for attachment to the cytoplasmic membrane. J. Biol. Chem. 264:1640316410.
11. Bossemeyer, D.,, A. Schlosser,, and E. P. Bakker. 1989b. Specific cesium transport via the Escherichia coli Kup (TrkD) K+ uptake system. J. Bacteriol. 171:22192221.
12. Chang, G.,, R. H. Spencer,, A. T. Lee,, M. T. Barclay,, and D. C. Rees. 1998. Structure of the MscL homolog from Mycobacterium tuberculosis: a gated mechanosensitive ion channel. Science 282:22202226.
13. Choe, S.,, and T. Roosild. 2002. Regulation of the K channels by cytoplasmic domains. Biopolymers 66:294299.
14. Cortes, D. M.,, L. G. Cuello,, and E. Perozo. 2001. Molecular architecture of full-length KcsA: role of cytoplasmic domains in ion permeation and activation gating. J. Gen. Physiol. 117:165180.
15. Doyle, D. A.,, J. M. Cabral,, R. A. Pfuetzner,, A. L. Kuo,, J. M. Gulbis,, S. L. Cohen,, B. T. Chait,, and R. Mac-Kinnon. 1998. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science 280:6977.
16. Durell, S. R.,, E. P. Bakker,, and H. R. Guy. 2000. Does the KdpA subunit from the high affinity K+-translocating P-type KDP-ATPase have a structure similar to that of K+ channels? Biophys. J. 78:188199.
17. Durell, S. R.,, Y. L. Hao,, T. Nakamura,, E. P. Bakker,, and H. R. Guy. 1999. Evolutionary relationship between K+ channels and symporters. Biophys. J. 77:775788.
18. Dutzler, R.,, E. B. Campbell,, M. Cadene,, B. T. Chait,, and R. MacKinnon. 2002. X-ray structure of a CIC chloride channel at 3.0 angstrom reveals the molecular basis of anion selectivity. Nature 415:287294.
19. Elmore, M. J.,, A. J. Lamb,, G. Y. Ritchie,, R. M. Douglas,, A. Munro,, A. Gajewska,, and I. R. Booth. 1990. Activation of potassium efflux from Escherichia coli by glutathione metabolites. Mol. Microbiol. 4:405412.
20. Epstein, W. 2003. The roles and regulation of potassium in bacteria. Prog. Nucleic Acid Res. Mol. Biol. 75:293320.
21. Epstein, W.,, and B. S. Kim. 1971. Potassium transport loci in Escherichia coli K-12. J. Bacteriol. 108:639644.
22. Faig, M.,, M. A. Bianchet,, P. Talalay,, S. Chen,, S. Winski,, D. Ross,, and L. M. Amzel. 2000. Structures of recombinant human and mouse NAD(P)H:quinone oxidoreductases: species comparison and structural changes with substrate binding and release. Proc. Natl. Acad. Sci. USA 97:31773182.
23. Ferguson, G. P.,, A. W. Munro,, R. M. Douglas,, D. Mclaggan,, and I. R. Booth. 1993. Activation of potassium channels during metabolite detoxification in Escherichia coli. Mol. Microbiol. 9:12971303.
24. Ferguson, G. P.,, S. Totemeyer,, M. J. MacLean,, and I. R. Booth. 1998. Methylglyoxal production in bacteria: suicide or survival? Arch. Microbiol. 170:209218.
25. Fujisawa, M.,, Y. Wada,, and M. Ito. 2004. Modulation of the K+ efflux activity of Bacillus subtilis YhaU by YhaT and the C-terminal region of YhaS. FEMS Microbiol. Lett. 231:211217.
26. Hamann, A.,, D. Bossemeyer,, and E. P. Bakker. 1987. Physical mapping of the K+ transport trkA gene of Escherichia coli and overproduction of the TrkA protein. J. Bacteriol. 169:31383145.
27. Harms, C.,, Y. Domoto,, C. Celik,, E. Rahe,, S. Stumpe,, R. Schmid,, T. Nakamura,, and E. P. Bakker. 2001. Identification of the ABC protein SapD as the subunit that confers ATP dependence to the K+-uptake systems Trk(H) and Trk(G) from Escherichia coli K-12. Microbiology 147:29913003.
28. Holtmann, G.,, E. P. Bakker,, N. Uozumi,, and E. Bremer. 2003. KtrAB and KtrCD: two K+ uptake systems in Bacillus subtilis and their role in adaptation to hypertonicity. J. Bacteriol. 185:12891298.
29. Jiang, Y. X.,, A. Lee,, J. Y. Chen,, M. Cadene,, B. T. Chait,, and R. MacKinnon. 2002a. Crystal structure and mechanism of a calcium-gated potassium channel. Nature 417:515522.
30. Jiang, Y. X.,, A. Lee,, J. Y. Chen,, M. Cadene,, B. T. Chait,, and R. MacKinnon. 2002b. The open pore conformation of potassium channels. Nature 417:523526.
31. Jiang, Y. X.,, A. Lee,, J. Y. Chen,, V. Ruta,, M. Cadene,, B. T. Chait,, and R. MacKinnon. 2003. X-ray structure of a voltage-dependent K+ channel. Nature 423:3341.
32. Jiang, Y. X.,, A. Pico,, M. Cadene,, B. T. Chait,, and R. MacKinnon. 2001. Structure of the RCK domain from the E. coli K+ channel and demonstration of its presence in the human BK channel. Neuron 29:593601.
Kuo, A.,, J. M. Gulbis,, J. F. Antcliff,, T. Rahman,, E. D. Lowe,, J. Zimmer,, J. Cuthbertson,, F. M. Ashcroft,, T. Ezaki,, and D. A. Doyle. 2003.a. Crystal structure of the potassium channel KirBac1.1 in the closed state. Science 300:19221926.
34. Kuo, M. M. C.,, Y. Saimi,, and C. Kung. 2003b. Gain-of-function mutations indicate that Escherichia coli Kch forms a functional K+ conduit in vivo. EMBO J. 22:40494058.
35. Kyte, J.,, and R. F. Doolittle. 1982. A simple method for displaying the hydropathic character of a protein. J. Mol. Biol. 157:105132.
36. Li, R.,, M. A. Bianchet,, P. Talalay,, and L. M. Amzel. 1995. The 3-dimensional structure of Nad(P)H:quinone reductase, a flavoprotein involved in cancer chemoprotection and chemotherapy: mechanism of the 2-electron reduction. Proc. Natl. Acad. Sci. USA 92:88468850.
37. Liu, Y. S.,, P. Sompornpisut,, and E. Perozo. 2001. Structure of the KcsA channel intracellular gate in the open state. Nat. Struct. Biol. 8:883887.
38. Mackinnon, R. 2000. Mechanism of ion conduction and selectivity in K channels. J. Gen. Physiol. 116:17.
39. MacLean, M. J.,, L. S. Ness,, G. P. Ferguson,, and I. R. Booth. 1998. The role of glyoxalase I in the detoxification of methylglyoxal and in the activation of the KefB K+ efflux system in Escherichia coli. Mol. Microbiol. 27:563571.
40. Martz, E. 2002. Protein explorer: easy yet powerful macromolecular visualization. Trends Biochem. Sci. 27:107109.
41. McLaggan, D.,, H. Rufino,, M. Jaspars,, and I. R. Booth. 2000. Glutathione-dependent conversion of N-ethylmaleimide to the maleamic acid by Escherichia coli: an intracellular detoxification process. Appl. Environ. Microbiol. 66:13931399.
42. Meury, J.,, and A. Kepes. 1982. Glutathione and the gated potassium channels of Escherichia coli. EMBO J. 1:339343.
43. Meury, J.,, S. Lebail,, and A. Kepes. 1980. Opening of potassium channels in Escherichia coli membranes by thiol reagents and recovery of potassium tightness. Eur. J. Biochem. 113:3338.
44. Miller, S.,, R. M. Douglas,, P. Carter,, and I. R. Booth. 1997. Mutations in the glutathione-gated KefC K+ efflux system of Escherichia coli that cause constitutive activation. J. Biol. Chem. 272:2494224947.
45. Miller, S.,, L. S. Ness,, C. M. Wood,, B. C. Fox,, and I. R. Booth. 2000. Identification of an ancillary protein, YabF, required for activity of the KefC glutathione-gated potassium efflux system in Escherichia coli. J. Bacteriol. 182:65366540.
46. Morais-Cabral, J. H.,, Y. F. Zhou,, and R. MacKinnon. 2001. Energetic optimization of ion conduction rate by the K+ selectivity filter. Nature 414:3742.
47. Moras, D.,, K. W. Olsen,, M. N. Sabesan,, M. Buehner,, G. C. Ford,, and M. G. Rossmann. 1975. Studies of asymmetry in the three-dimensional structure of lobster D-glyceraldehyde-3-phosphate dehydrogenase. J. Biol. Chem. 250:91379162.
48. Munro, A. W.,, G. Y. Ritchie,, A. J. Lamb,, R. M. Douglas,, and I. R. Booth. 1991. The cloning and DNA sequence of the gene for the glutathione-regulated potassium-efflux system KefC of Escherichia coli. Mol. Microbiol. 5:607616.
49. Nakamura, C.,, J. G. Burgess,, K. Sode,, and T. Matsunaga. 1995. An iron-regulated gene, MagA, encoding an iron transport protein of Magnetospirillum sp. strain Amb-1. J. Biol. Chem. 270:2839228396.
50. Nakamura, T.,, R. Yuda,, T. Unemoto,, and E. P. Bakker. 1998. KtrAB, a new type of bacterial K+-uptake system from Vibrio alginolyticus. J. Bacteriol. 180:34913494.
51. Ness, L. S.,, and I. R. Booth. 1999. Different foci for the regulation of the activity of the KefB and KefC glutathione-gated K+ efflux systems. J. Biol. Chem. 274:95249530.
52. Padan, E.,, and S. Schuldiner. 1994. Molecular biology of Na+/H+ antiporters: molecular devices that couple the Na+ and H+ circulation in cells. Biochim. Biophys. Acta 1187:206210.
53. Puder, M.,, and S. Soberman. 1997. Glutathione conjugates recognize the Rossmann fold of glyceraldehyde-3-phosphate dehydrogenase. J. Biol. Chem. 272:1093610940.
54. Ramirez, J.,, O. Ramirez,, C. Saldana,, R. Coria,, and A. Pena. 1998. A Saccharomyces cerevisiae mutant lacking a K+/H+ exchanger. J. Bacteriol. 180:58605865.
55. Reizer, J.,, A. Reizer,, and M. H. Saier. 1992. The putative Na+/H+ antiporter (NapA) of Enterococcus hirae is homologous to the putative K+/H+ antiporter (KefC) of Escherichia coli. FEMS Microbiol. Lett. 94:161164.
56. Rhoads, D. B.,, and W. Epstein. 1977. Energy coupling to net K+ transport in Escherichia coli K-12. J. Biol. Chem. 253:13941401.
57. Rhoads, D. B.,, and W. Epstein. 1978. Cation transport in Escherichia coli. IX. Regulation of K+ transport. J. Gen. Physiol. 72:283295.
58. Rhoads, D. B.,, L. Laimins,, and W. Epstein. 1978. Functional organization of the kdp genes of Escherichia coli K-12. J. Bacteriol. 135:445452.
59. Roe, A. J.,, D. McLaggan,, C. P. O’Byrne,, and I. R. Booth. 2000. Rapid inactivation of the Escherichia coli Kdp K+ uptake system by high potassium concentrations. Mol. Microbiol. 35:12351243.
60. Roosild, T. P.,, S. Miller,, I. R. Booth,, and S. Choe. 2002. A mechanism of regulating transmembrane potassium flux through a ligand-mediated conformational switch. Cell 109:781791.
61. Roux, B.,, and R. MacKinnon. 1999. The cavity and pore helices the KcsA K+ channel: electrostatic stabilization of monovalent cations. Science 285:100102.
62. Saier, M. H.,, B. H. Eng,, S. Fard,, J. Garg,, D. A. Haggerty,, W. J. Hutchinson,, D. L. Jack,, E. C. Lai,, H. J. Liu,, D. P. Nusinew,, A. M. Omar,, S. S. Pao,, I. T. Paulsen,, J. A. Quan,, M. Sliwinski,, T. T. Tseng,, S. Wachi,, and G. B. Young. 1999. Phylogenetic characterization of novel transport protein families revealed by genome analyses. Biochim. Biophys. Acta 1422:156.
63. Schleyer, M.,, and E. P. Bakker. 1993. Nucleotide sequence and 3′-end deletion studies indicate that the K+-uptake protein Kup from Escherichia coli is composed of a hydrophobic core linked to a large and partially essential hydrophilic C terminus. J. Bacteriol. 175:69256931.
64. Schlosser, A.,, A. Hamann,, D. Bossemeyer,, E. Schneider,, and E. P. Bakker. 1993. NAD+ binding to the Escherichia coli K+-uptake protein TrkA and sequence similarity between TrkA and domains of a family of dehydrogenases suggest a role for NAD+in bacterial transport. Mol. Microbiol. 9:533543.
65. Schlosser, A.,, M. Meldorf,, S. Stumpe,, E. P. Bakker,, and W. Epstein. 1995. TrkH and its homolog, TrkG, determine the specificity and kinetics of cation-transport by the Trk system of Escherichia coli. J. Bacteriol. 177:19081910.
66. Southworth, T. W.,, A. A. Guffanti,, A. Moir,, and T. A. Krulwich. 2001. GerN, an endospore germination protein of Bacillus cereus, is an Na+/H+-K+ antiporter. J. Bacteriol. 183:58965903.
67. Stewart, L. M. D.,, E. P. Bakker,, and I. R. Booth. 1985. Energy coupling to K+ uptake via the Trk system in Escherichia coli: the role of ATP. J. Gen. Microbiol. 131:7785.
68. Tholema, N.,, E. P. Bakker,, A. Suzuki,, and T. Nakamura. 1999. Change to alanine of one out of four selectivity filter glycines in KtrB causes a two orders of magnitude decrease in the affinities for both K+ and Na+of the Na+dependent K+ uptake system KtrAB from Vibrio alginolyticus. FEBS Lett. 450:217220.
69. Wei, Y.,, T. W. Southworth,, H. Kloster,, M. Ito,, A. A. Guffanti,, A. Moir,, and T. A. Krulwich. 2003. Mutational loss of a K+ and transporter affects the growth and endospore formation of alkaliphilic Bacillus pseudofirmus OF4. J. Bacteriol. 185:51335147.
70. Wood, J. M. 1999. Osmosensing by bacteria: signals and membrane-based sensors. Microbiol. Mol. Biol. Rev. 63:230262.
71. Zhou, Y. F.,, J. H. Morais-Cabral,, A. Kaufman,, and R. MacKinnon. 2001. Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 angstrom resolution. Nature 414:4348.


Generic image for table
Table 1

Channels and transporters utilizing Ktn domains

Citation: Booth I, Edwards M, Gunasekera B, Li C, Miller S. 2005. The Ktn Domain and Its Role as a Channel and Transporter Regulator, p 21-40. In Kubalski A, Martinac B (ed), Bacterial Ion Channels and Their Eukaryotic Homologs. ASM Press, Washington, DC. doi: 10.1128/9781555816452.ch2

This is a required field
Please enter a valid email address
Please check the format of the address you have entered.
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error