Key Points
-
Inward rectifier potassium (Kir) channels are an important class of potassium channels with the simplest structural architecture of the characterized eukaryotic channels. This review highlights the convergence of structural studies and functional analyses of this large and extensively analysed ion channel family.
-
Several high-resolution structures of bacterial K+ channels have been solved: KcsA, MthK, KvAP and KirBac1.1. The recent structure of KirBac1.1, which has high sequence homology with eukaryotic Kir channels, offers the opportunity to evaluate the results of functional assays in the context of the relevant channel structure.
-
The selectivity filter confers selectivity for K+ by coordinating the ions with the backbone carbonyl oxygens of the K+ channel signature sequence. In Kir channels, structural features other than the signature sequence are also important for K+ selectivity.
-
Inward rectification refers to the preferential flow of ions into the cell. In Kir channels, outward flow of K+ is impeded by a block of the pore by cytoplasmic polyamines and Mg2+. The long cytoplasmic pore that was revealed in the high-resolution structures of KirBac1.1 and the intracellular domain of Kir3.1 explain several of the characteristics of inward rectification that have been identified in functional studies.
-
Kir channels can change their conformation and thereby reduce ion flow through them, which is referred to as gating. Two locations for the gate have been proposed: the bundle crossing and the selectivity filter. Conformational changes at these two locations might correspond to the functionally observed slow and fast gating, respectively.
-
Gating of Kir channels is regulated by several cytoplasmic factors, including PtdIns(4,5)P2, arachidonic acid, Na+ and Mg2+ ions, pH, heterotrimeric G proteins, ATP, phosphorylation, oxidation/reduction and interactions with PDZ domains. Mapping the functionally identified sites of interaction between Kir channels and these modulators onto the cytoplasmic structures of Kir3.1 and KirBac1.1 provides insights into the complex and synergic mechanisms of Kir channel modulation.
-
A challenging area for future explorations concerns the structural rearrangements that are induced by the binding of intracellular modulators and how they translate into opening and closing of the channel.
Abstract
Inwardly rectifying K+ (Kir) channels have a wide range of functions including the control of neuronal signalling, heart rate, blood flow and insulin release. Because of the physiological importance of these channels, considerable effort has been invested in understanding the structural basis of their physiology. In this review, we use two recent, high-resolution structures as foundations for examining our current understanding of the fundamental functions that are shared by all K+ channels, such as K+ selectivity and channel gating, as well as characteristic features of Kir channel family members, such as inward rectification and their regulation by intracellular factors.
This is a preview of subscription content, access via your institution
Access options
Subscribe to this journal
Receive 12 print issues and online access
$189.00 per year
only $15.75 per issue
Buy this article
- Purchase on SpringerLink
- Instant access to full article PDF
Prices may be subject to local taxes which are calculated during checkout
Similar content being viewed by others
Accession codes
References
Shieh, C. C., Coghlan, M., Sullivan, J. P. & Gopalakrishnan, M. Potassium channels: molecular defects, diseases, and therapeutic opportunities. Pharmacol. Rev. 52, 557–594 (2000).
Yang, J., Jan, Y. N. & Jan, L. Y. Determination of the subunit stoichiometry of an inwardly rectifying potassium channel. Neuron 15, 1441–1447 (1995).
Raab-Graham, K. F. & Vandenberg, C. A. Tetrameric subunit structure of the native brain inwardly rectifying potassium channel Kir2.2. J. Biol. Chem. 273, 19699–19707 (1998).
Kuo, A. et al. Crystal structure of the potassium channel KirBac1.1 in the closed state. Science 300, 1922–1926 (2003). The first X-ray crystal structure of a Kir channel, showing both the transmembrane and cytoplasmic regions of the same K+ channel.
Doyle, D. A. et al. The structure of the potassium channel: molecular basis of K+ conduction and selectivity. Science 280, 69–77 (1998).
Morais-Cabral, J. H., Zhou, Y. & MacKinnon, R. Energetic optimization of ion conduction rate by the K+ selectivity filter. Nature 414, 37–42 (2001).
Zhou, Y., Morais-Cabral, J. H., Kaufman, A. & MacKinnon, R. Chemistry of ion coordination and hydration revealed by a K+ channel-Fab complex at 2.0 Å resolution. Nature 414, 43–48 (2001).
Jiang, Y. et al. Crystal structure and mechanism of a calcium-gated potassium channel. Nature 417, 515–522 (2002).
Jiang, Y. et al. X-ray structure of a voltage-dependent K+ channel. Nature 423, 33–41 (2003).
Cohen, B. E., Grabe, M. & Jan, L. Y. Answers and questions from the KvAP structures. Neuron 39, 395–400 (2003).
Nishida, M. & MacKinnon, R. Structural basis of inward rectification: cytoplasmic pore of the G protein-gated inward rectifier GIRK1 at 1.8 Å resolution. Cell 111, 957–965 (2002). This article reports the first view of the large cytoplasmic pore of a mammalian Kir channel.
Minor, D. L. Jr, Masseling, S. J., Jan, Y. N. & Jan, L. Y. Transmembrane structure of an inwardly rectifying potassium channel. Cell 96, 879–891 (1999). This paper uses a yeast screen for functional K+ channels to probe the local environment of residues in the transmembrane helices of Kir2. 1.
Lu, T., Nguyen, B., Zhang, X. & Yang, J. Architecture of a K+ channel inner pore revealed by stoichiometric covalent modification. Neuron 22, 571–580 (1999).
Thompson, G. A., Leyland, M. L., Ashmole, I., Sutcliffe, M. J. & Stanfield, P. R. Residues beyond the selectivity filter of the K+ channel Kir2.1 regulate permeation and block by external Rb+ and Cs+. J. Physiol. (Lond.) 526, 231–240 (2000).
Durell, S. R. & Guy, H. R. A family of putative Kir potassium channels in prokaryotes. BMC Evol. Biol. 1, 14 (2001).
Heginbotham, L., Lu, Z., Abramson, T. & MacKinnon, R. Mutations in the K+ channel signature sequence. Biophys. J. 66, 1061–1067 (1994).
Patil, N. et al. A potassium channel mutation in weaver mice implicates membrane excitability in granule cell differentiation. Nature Genet. 11, 126–129 (1995).
Slesinger, P. A. et al. Functional effects of the mouse weaver mutation on G protein-gated inwardly rectifying K+ channels. Neuron 16, 321–331 (1996).
Navarro, B. et al. Nonselective and G βγ-insensitive weaver K+ channels. Science 272, 1950–1953 (1996).
Kofuji, P. et al. Functional analysis of the weaver mutant GIRK2 K+ channel and rescue of weaver granule cells. Neuron 16, 941–952 (1996).
Berneche, S. & Roux, B. Energetics of ion conduction through the K+ channel. Nature 414, 73–77 (2001).
Berneche, S. & Roux, B. Molecular dynamics of the KcsA K+ channel in a bilayer membrane. Biophys. J. 78, 2900–2917 (2000).
Shrivastava, I. H., Tieleman, D. P., Biggin, P. C. & Sansom, M. S. K+ versus Na+ ions in a K+ channel selectivity filter: a simulation study. Biophys. J. 83, 633–645 (2002).
Aqvist, J. & Luzhkov, V. Ion permeation mechanism of the potassium channel. Nature 404, 881–884 (2000).
Choe, S. Potassium channel structures. Nature Rev. Neurosci. 3, 115–121 (2002). An extensive review of the mechanisms of ion selectivity and permeation in K+ channels.
Lu, Z., Klem, A. M. & Ramu, Y. Ion conduction pore is conserved among potassium channels. Nature 413, 809–813 (2001).
Slesinger, P. A. Ion selectivity filter regulates local anesthetic inhibition of G-protein-gated inwardly rectifying K+ channels. Biophys. J. 80, 707–718 (2001).
Yi, B. A., Lin, Y. F., Jan, Y. N. & Jan, L. Y. Yeast screen for constitutively active mutant G protein-activated potassium channels. Neuron 29, 657–667 (2001).
Yang, J., Yu, M., Jan, Y. N. & Jan, L. Y. Stabilization of ion selectivity filter by pore loop ion pairs in an inwardly rectifying potassium channel. Proc. Natl Acad. Sci. USA 94, 1568–1572 (1997).
Kubo, Y. Two aspects of the inward rectification mechanism. Effects of cytoplasmic blockers and extracellular K+ on the inward rectifier K+ channel. Jpn Heart J. 37, 631–641 (1996).
Shieh, R. C., Chang, J. C. & Kuo, C. C. K+ binding sites and interactions between permeating K+ ions at the external pore mouth of an inward rectifier K+ channel (Kir2.1). J. Biol. Chem. 274, 17424–17430 (1999).
Dibb, K. M. et al. Molecular basis of ion selectivity, block and rectification of the inward rectifier Kir3.1/Kir3.4 K+ channel. J. Biol. Chem. 22 September 2003 (doi: 10.1074/jbc.M307723200).
Krapivinsky, G. et al. A novel inward rectifier K+ channel with unique pore properties. Neuron 20, 995–1005 (1998).
Vandenberg, C. A. Inward rectification of a potassium channel in cardiac ventricular cells depends on internal magnesium ions. Proc. Natl Acad. Sci. USA 84, 2560–2564 (1987).
Matsuda, H., Saigusa, A. & Irisawa, H. Ohmic conductance through the inwardly rectifying K+ channel and blocking by internal Mg2+. Nature 325, 156–159 (1987).
Lopatin, A. N., Makhina, E. N. & Nichols, C. G. Potassium channel block by cytoplasmic polyamines as the mechanism of intrinsic rectification. Nature 372, 366–369 (1994).
Lu, Z. & MacKinnon, R. Electrostatic tuning of Mg2+ affinity in an inward-rectifier K+ channel. Nature 371, 243–246 (1994).
Stanfield, P. R. et al. A single aspartate residue is involved in both intrinsic gating and blockage by Mg2+ of the inward rectifier, IRK1. J. Physiol. (Lond.) 478, 1–6 (1994).
Wible, B. A., Taglialatela, M., Ficker, E. & Brown, A. M. Gating of inwardly rectifying K+ channels localized to a single negatively charged residue. Nature 371, 246–249 (1994).
Yang, J., Jan, Y. N. & Jan, L. Y. Control of rectification and permeation by residues in two distinct domains in an inward rectifier K+ channel. Neuron 14, 1047–1054 (1995).
Fujiwara, Y. & Kubo, Y. Ser165 in the second transmembrane region of the Kir2.1 channel determines its susceptibility to blockade by intracellular Mg2+. J. Gen. Physiol. 120, 677–693 (2002).
Taglialatela, M., Wible, B. A., Caporaso, R. & Brown, A. M. Specification of pore properties by the carboxyl terminus of inwardly rectifying K+ channels. Science 264, 844–847 (1994).
Taglialatela, M., Ficker, E., Wible, B. A. & Brown, A. M. C-terminus determinants for Mg2+ and polyamine block of the inward rectifier K+ channel IRK1. EMBO J. 14, 5532–5541 (1995).
Baukrowitz, T. et al. Inward rectification in KATP channels: a pH switch in the pore. EMBO J. 18, 847–853 (1999).
Kubo, Y. & Murata, Y. Control of rectification and permeation by two distinct sites after the second transmembrane region in Kir2.1 K+ channel. J. Physiol. (Lond.) 531, 645–660 (2001).
Lopatin, A. N., Makhina, E. N. & Nichols, C. G. The mechanism of inward rectification of potassium channels: 'long-pore plugging' by cytoplasmic polyamines. J. Gen. Physiol. 106, 923–955 (1995).
Lee, J. K., John, S. A. & Weiss, J. N. Novel gating mechanism of polyamine block in the strong inward rectifier K+ channel Kir2.1. J. Gen. Physiol. 113, 555–564 (1999).
Xie, L. H., John, S. A. & Weiss, J. N. Spermine block of the strong inward rectifier potassium channel Kir2.1: dual roles of surface charge screening and pore block. J. Gen. Physiol. 120, 53–66 (2002).
Xie, L. H., John, S. A. & Weiss, J. N. Inward rectification by polyamines in mouse Kir2.1 channels: synergy between blocking components. J. Physiol. (Lond.) 550, 67–82 (2003).
Pearson, W. L. & Nichols, C. G. Block of the Kir2.1 channel pore by alkylamine analogues of endogenous polyamines. J. Gen. Physiol. 112, 351–363 (1998).
Guo, D., Ramu, Y., Klem, A. M. & Lu, Z. Mechanism of rectification in inward-rectifier K+ channels. J. Gen. Physiol. 121, 261–276 (2003).
Spassova, M. & Lu, Z. Coupled ion movement underlies rectification in an inward-rectifier K+ channel. J. Gen. Physiol. 112, 211–221 (1998).
Perozo, E., Cortes, D. M. & Cuello, L. G. Structural rearrangements underlying K+-channel activation gating. Science 285, 73–78 (1999).
Phillips, L. R., Enkvetchakul, D. & Nichols, C. G. Gating dependence of inner pore access in inward rectifier K+ channels. Neuron 37, 953–962 (2003). This SCAM study points out an important caveat of the SCAM technique, namely that the modifying agent can be trapped in the pore of the closed channel.
Sadja, R., Smadja, K., Alagem, N. & Reuveny, E. Coupling Gβγ-dependent activation to channel opening via pore elements in inwardly rectifying potassium channels. Neuron 29, 669–680 (2001).
Liu, Y. S., Sompornpisut, P. & Perozo, E. Structure of the KcsA channel intracellular gate in the open state. Nature Struct. Biol. 8, 883–887 (2001).
Jiang, Y. et al. The open pore conformation of potassium channels. Nature 417, 523–526 (2002). This paper provided the first structural evidence for bending of the M2 helices at a glycine hinge as a possible gating mechanism for K+ channels.
Jin, T. et al. The βγ subunits of G proteins gate a K+ channel by pivoted bending of a transmembrane segment. Mol. Cell 10, 469–481 (2002).
Liu, Y., Holmgren, M., Jurman, M. E. & Yellen, G. Gated access to the pore of a voltage-dependent K+ channel. Neuron 19, 175–184 (1997).
del Camino, D. & Yellen, G. Tight steric closure at the intracellular activation gate of a voltage-gated K+ channel. Neuron 32, 649–656 (2001).
Rothberg, B. S., Shin, K. S., Phale, P. S. & Yellen, G. Voltage-controlled gating at the intracellular entrance to a hyperpolarization-activated cation channel. J. Gen. Physiol. 119, 83–91 (2002).
Flynn, G. E. & Zagotta, W. N. Conformational changes in S6 coupled to the opening of cyclic nucleotide-gated channels. Neuron 30, 689–698 (2001).
Flynn, G. E., Johnson, J. P. Jr & Zagotta, W. N. Cyclic nucleotide-gated channels: shedding light on the opening of a channel pore. Nature Rev. Neurosci. 2, 643–651 (2001).
Loussouarn, G., Makhina, E. N., Rose, T. & Nichols, C. G. Structure and dynamics of the pore of inwardly rectifying KATP channels. J. Biol. Chem. 275, 1137–1144 (2000).
Xiao, J., Zhen, X. G. & Yang, J. Localization of PIP2 activation gate in inward rectifier K+ channels. Nature Neurosci. 6, 811–818 (2003).
Starkus, J. G., Kuschel, L., Rayner, M. D. & Heinemann, S. H. Ion conduction through C-type inactivated Shaker channels. J. Gen. Physiol. 110, 539–550 (1997).
Kiss, L., LoTurco, J. & Korn, S. J. Contribution of the selectivity filter to inactivation in potassium channels. Biophys. J. 76, 253–263 (1999).
Zheng, J. & Sigworth, F. J. Selectivity changes during activation of mutant Shaker potassium channels. J. Gen. Physiol. 110, 101–117 (1997).
Liu, Y., Jurman, M. E. & Yellen, G. Dynamic rearrangement of the outer mouth of a K+ channel during gating. Neuron 16, 859–867 (1996).
Loots, E. & Isacoff, E. Y. Molecular coupling of S4 to a K+ channel's slow inactivation gate. J. Gen. Physiol. 116, 623–636 (2000).
Capener, C. E. et al. Homology modeling and molecular dynamics simulation studies of an inward rectifier potassium channel. Biophys. J. 78, 2929–2942 (2000).
Capener, C. E., Proks, P., Ashcroft, F. M. & Sansom, M. S. Filter flexibility in a mammalian K+ channel: models and simulations of Kir6.2 mutants. Biophys. J. 84, 2345–2356 (2003).
Capener, C. E., Kim, H. J., Arinaminpathy, Y. & Sansom, M. S. Ion channels: structural bioinformatics and modelling. Hum. Mol. Genet. 11, 2425–2433 (2002).
Lu, T., Wu, L., Xiao, J. & Yang, J. Permeant ion-dependent changes in gating of Kir2.1 inward rectifier potassium channels. J. Gen. Physiol. 118, 509–522 (2001).
Choe, H., Sackin, H. & Palmer, L. G. Permeation and gating of an inwardly rectifying potassium channel. Evidence for a variable energy well. J. Gen. Physiol. 112, 433–446 (1998).
Guo, L. & Kubo, Y. Comparison of the open-close kinetics of the cloned inward rectifier K+ channel IRK1 and its point mutant (Q140E) in the pore region. Receptors Channels 5, 273–289 (1998).
Proks, P., Capener, C. E., Jones, P. & Ashcroft, F. M. Mutations within the P-loop of Kir6.2 modulate the intraburst kinetics of the ATP-sensitive potassium channel. J. Gen. Physiol. 118, 341–353 (2001).
Chan, K. W., Sui, J. L., Vivaudou, M. & Logothetis, D. E. Control of channel activity through a unique amino acid residue of a G protein-gated inwardly rectifying K+ channel subunit. Proc. Natl Acad. Sci. USA 93, 14193–14198 (1996).
So, I., Ashmole, I., Davies, N. W., Sutcliffe, M. J. & Stanfield, P. R. The K+ channel signature sequence of murine Kir2.1: mutations that affect microscopic gating but not ionic selectivity. J. Physiol. (Lond.) 531, 37–50 (2001).
Lu, T. et al. Probing ion permeation and gating in a K+ channel with backbone mutations in the selectivity filter. Nature Neurosci. 4, 239–246 (2001). Using hydroxy acids, this study introduced changes in the backbone of the K+ channel signature sequence and found that channel gating, but not selectivity, is altered.
Enkvetchakul, D., Loussouarn, G., Makhina, E., Shyng, S. L. & Nichols, C. G. The kinetic and physical basis of KATP channel gating: toward a unified molecular understanding. Biophys. J. 78, 2334–2348 (2000).
Choe, H., Sackin, H. & Palmer, L. G. Permeation properties of inward-rectifier potassium channels and their molecular determinants. J. Gen. Physiol. 115, 391–404 (2000).
Choe, H., Sackin, H. & Palmer, L. G. Gating properties of inward-rectifier potassium channels: effects of permeant ions. J. Membr. Biol. 184, 81–89 (2001).
Trapp, S., Proks, P., Tucker, S. J. & Ashcroft, F. M. Molecular analysis of ATP-sensitive K+ channel gating and implications for channel inhibition by ATP. J. Gen. Physiol. 112, 333–349 (1998).
Tucker, S. J. et al. Molecular determinants of KATP channel inhibition by ATP. EMBO J. 17, 3290–3296 (1998).
Huang, C. L., Feng, S. & Hilgemann, D. W. Direct activation of inward rectifier potassium channels by PIP2 and its stabilization by Gβγ. Nature 391, 803–806 (1998).
Sui, J. L., Petit-Jacques, J. & Logothetis, D. E. Activation of the atrial KACh channel by the βγ subunits of G proteins or intracellular Na+ ions depends on the presence of phosphatidylinositol phosphates. Proc. Natl Acad. Sci. USA 95, 1307–1312 (1998).
Petit-Jacques, J., Sui, J. L. & Logothetis, D. E. Synergistic activation of G protein-gated inwardly rectifying potassium channels by the βγ subunits of G proteins and Na+ and Mg2+ ions. J. Gen. Physiol. 114, 673–684 (1999).
Baukrowitz, T. et al. PIP2 and PIP as determinants for ATP inhibition of KATP channels. Science 282, 1141–1144 (1998).
Shyng, S. L. & Nichols, C. G. Membrane phospholipid control of nucleotide sensitivity of KATP channels. Science 282, 1138–1141 (1998).
Shyng, S. L., Cukras, C. A., Harwood, J. & Nichols, C. G. Structural determinants of PIP2 regulation of inward rectifier KATP channels. J. Gen. Physiol. 116, 599–608 (2000).
Soom, M. et al. Multiple PIP2 binding sites in Kir2.1 inwardly rectifying potassium channels. FEBS Lett. 490, 49–53 (2001).
Lopes, C. M. et al. Alterations in conserved Kir channel-PIP2 interactions underlie channelopathies. Neuron 34, 933–944 (2002). An extensive mutagenesis study investigating the contribution of basic amino acids to PtdIns(4,5)P 2 affinity in Kir2.1 and 1.1. In addition, the authors test the effects of mutations in Kir2.1 and 1.1 underlying channelopathies on PtdIns(4,5)P 2 binding.
Zhang, H., He, C., Yan, X., Mirshahi, T. & Logothetis, D. E. Activation of inwardly rectifying K+ channels by distinct PtdIns(4,5)P2 interactions. Nature Cell Biol. 1, 183–188 (1999).
Prescott, E. D. & Julius, D. A modular PIP2 binding site as a determinant of capsaicin receptor sensitivity. Science 300, 1284–1288 (2003).
Schulze, D., Krauter, T., Fritzenschaft, H., Soom, M. & Baukrowitz, T. Phosphatidylinositol 4,5-bisphosphate (PIP2) modulation of ATP and pH sensitivity in Kir channels. A tale of an active and a silent PIP2 site in the N terminus. J. Biol. Chem. 278, 10500–10505 (2003).
Stanfield, P. R., Nakajima, S. & Nakajima, Y. Constitutively active and G-protein coupled inward rectifier K+ channels: Kir2.0 and Kir3.0. Rev. Physiol. Biochem. Pharmacol. 145, 47–179 (2002). An extensive review on Kir2 and Kir3 channels.
Sadja, R., Alagem, N. & Reuveny, E. Gating of GIRK channels: details of an intricate, membrane-delimited signaling complex. Neuron 39, 9–12 (2003).
Huang, C. L., Slesinger, P. A., Casey, P. J., Jan, Y. N. & Jan, L. Y. Evidence that direct binding of Gβγ to the GIRK1 G protein-gated inwardly rectifying K+ channel is important for channel activation. Neuron 15, 1133–1143 (1995).
Kunkel, M. T. & Peralta, E. G. Identification of domains conferring G protein regulation on inward rectifier potassium channels. Cell 83, 443–449 (1995).
Huang, C. L., Jan, Y. N. & Jan, L. Y. Binding of the G protein βγ subunit to multiple regions of G protein-gated inward-rectifying K+ channels. FEBS Lett. 405, 291–298 (1997).
Krapivinsky, G. et al. Gβ binding to GIRK4 subunit is critical for G protein-gated K+ channel activation. J. Biol. Chem. 273, 16946–16952 (1998).
He, C. et al. Identification of critical residues controlling G protein-gated inwardly rectifying K+ channel activity through interactions with the βγ subunits of G proteins. J. Biol. Chem. 277, 6088–6096 (2002).
He, C., Zhang, H., Mirshahi, T. & Logothetis, D. E. Identification of a potassium channel site that interacts with G protein βγ subunits to mediate agonist-induced signaling. J. Biol. Chem. 274, 12517–12524 (1999).
Ivanina, T. et al. Mapping the Gβγ-binding sites in GIRK1 and GIRK2 subunits of the G protein-activated K+ channel. J. Biol. Chem. 278, 29174–29183 (2003).
Mirshahi, T., Mittal, V., Zhang, H., Linder, M. E. & Logothetis, D. E. Distinct sites on G protein βγ subunits regulate different effector functions. J. Biol. Chem. 277, 36345–36350 (2002).
Jiang, C., Qu, Z. & Xu, H. Gating of inward rectifier K+ channels by proton-mediated interactions of intracellular protein domains. Trends Cardiovasc. Med. 12, 5–13 (2002). Reviews the effects of pH on Kir channels and proposes a model of how protonation of cytoplasmic residues might lead to gating movements of the transmembrane domain.
Mao, J., Wu, J., Chen, F., Wang, X. & Jiang, C. Inhibition of G-protein-coupled inward rectifying K+ channels by intracellular acidosis. J. Biol. Chem. 278, 7091–7098 (2003).
Chanchevalap, S. et al. Involvement of histidine residues in proton sensing of ROMK1 channel. J. Biol. Chem. 275, 7811–7817 (2000).
Qu, Z. et al. Gating of inward rectifier K+ channels by proton-mediated interactions of N- and C-terminal domains. J. Biol. Chem. 275, 31573–31580 (2000).
Schulte, U. et al. pH gating of ROMK (Kir1.1) channels: control by an Arg-Lys-Arg triad disrupted in antenatal Bartter syndrome. Proc. Natl Acad. Sci. USA 96, 15298–15303 (1999).
Tucker, S. J., Gribble, F. M., Zhao, C., Trapp, S. & Ashcroft, F. M. Truncation of Kir6.2 produces ATP-sensitive K+ channels in the absence of the sulphonylurea receptor. Nature 387, 179–183 (1997).
Drain, P., Li, L. & Wang, J. KATP channel inhibition by ATP requires distinct functional domains of the cytoplasmic C terminus of the pore-forming subunit. Proc. Natl Acad. Sci. USA 95, 13953–13958 (1998).
Koster, J. C., Sha, Q., Shyng, S. & Nichols, C. G. ATP inhibition of KATP channels: control of nucleotide sensitivity by the N-terminal domain of the Kir6.2 subunit. J. Physiol. (Lond.) 515, 19–30 (1999).
Reimann, F., Ryder, T. J., Tucker, S. J. & Ashcroft, F. M. The role of lysine 185 in the Kir6.2 subunit of the ATP-sensitive channel in channel inhibition by ATP. J. Physiol. (Lond.) 520, 661–669 (1999).
Trapp, S., Haider, S., Jones, P., Sansom, M. S. & Ashcroft, F. M. Identification of residues contributing to the ATP binding site of Kir6.2. EMBO J. 22, 2903–2912 (2003).
Ho, I. H. & Murrell-Lagnado, R. D. Molecular mechanism for sodium-dependent activation of G protein-gated K+ channels. J. Physiol. (Lond.) 520, 645–651 (1999).
Ho, I. H. & Murrell-Lagnado, R. D. Molecular determinants for sodium-dependent activation of G protein-gated K+ channels. J. Biol. Chem. 274, 8639–8648 (1999).
Xu, H. et al. Distinct histidine residues control the acid-induced activation and inhibition of the cloned KATP channel. J. Biol. Chem. 276, 38690–38696 (2001).
Rogalski, S. L. & Chavkin, C. Eicosanoids inhibit the G-protein-gated inwardly rectifying potassium channel (Kir3) at the Na+/PIP2 gating site. J. Biol. Chem. 276, 14855–14860 (2001).
Wang, C., Wang, K., Wang, W., Cui, Y. & Fan, Z. Compromised ATP binding as a mechanism of phosphoinositide modulation of ATP-sensitive K+ channels. FEBS Lett. 532, 177–182 (2002).
MacGregor, G. G. et al. Nucleotides and phospholipids compete for binding to the C terminus of KATP channels. Proc. Natl Acad. Sci. USA 99, 2726–2731 (2002).
Kim, D. & Bang, H. Modulation of rat atrial G protein-coupled K+ channel function by phospholipids. J. Physiol. (Lond.) 517, 59–74 (1999).
Alagem, N., Yesylevskyy, S. & Reuveny, E. The pore helix is involved in stabilizing the open state of inwardly rectifying K+ channels. Biophys. J. 85, 300–312 (2003).
Proks, P., Antcliff, J. F. & Ashcroft, F. M. The ligand-sensitive gate of a potassium channel lies close to the selectivity filter. EMBO Rep. 4, 70–75 (2003).
Hommers, L. G., Lohse, M. J. & Bunemann, M. Regulation of the inward rectifying properties of G-protein-activated inwardly rectifying K+ (GIRK) channels by Gβγ subunits. J. Biol. Chem. 278, 1037–1043 (2003).
Schulte, U., Hahn, H., Wiesinger, H., Ruppersberg, J. P. & Fakler, B. pH-dependent gating of ROMK (Kir1.1) channels involves conformational changes in both N and C termini. J. Biol. Chem. 273, 34575–34579 (1998).
Riven, I., Kalmanzon, E., Segev, L. & Reuveny, E. Conformational rearrangements associated with the gating of the G protein-coupled potassium channel revealed by FRET microscopy. Neuron 38, 225–235 (2003). Using FRET and total internal reflection fluorescence microscopy, the authors observe that the distance between the cyan and yellow variants of the green fluorescent protein that are attached to the C and N termini of Kir3 channels changes after Gβγ-mediated activation of the channels.
Anderson, J. A., Huprikar, S. S., Kochian, L. V., Lucas, W. J. & Gaber, R. F. Functional expression of a probable Arabidopsis thaliana potassium channel in Saccharomyces cerevisiae. Proc. Natl Acad. Sci. USA 89, 3736–3740 (1992).
Sentenac, H. et al. Cloning and expression in yeast of a plant potassium ion transport system. Science 256, 663–665 (1992).
Tang, W. et al. Functional expression of a vertebrate inwardly rectifying K+ channel in yeast. Mol. Biol. Cell 6, 1231–1240 (1995).
Lodowski, D. T., Pitcher, J. A., Capel, W. D., Lefkowitz, R. J. & Tesmer, J. J. Keeping G proteins at bay: a complex between G protein-coupled receptor kinase 2 and Gβγ. Science 300, 1256–1262 (2003).
Palczewski, K. et al. Crystal structure of rhodopsin: a G protein-coupled receptor. Science 289, 739–745 (2000).
Doyle, D. A. et al. Crystal structures of a complexed and peptide-free membrane protein-binding domain: molecular basis of peptide recognition by PDZ. Cell 85, 1067–1076 (1996).
Clement, J. P. IV. et al. Association and stoichiometry of KATP channel subunits. Neuron 18, 827–838 (1997).
Locher, K. P., Lee, A. T. & Rees, D. C. The E. coli BtuCD structure: a framework for ABC transporter architecture and mechanism. Science 296, 1091–1098 (2002).
Humphrey, W., Dalke, A. & Schulten, K. VMD: visual molecular dynamics. J. Mol. Graph. 14, 33–38, 27–28 (1996).
Acknowledgements
We would like to thank D. Doyle for the coordinates of KirBac and communication on the structure. We would also like the thank members of the Jan laboratory for stimulating discussions and valuable comments on the review. F.A.H. is a student in the Neuroscience graduate program at UCSF. L.Y.J. is a HHMI investigator. This work was supported by an NIMH grant.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing financial interests.
Supplementary information
Related links
Related links
DATABASES
LocusLink
OMIM
Protein Data Bank
FURTHER INFORMATION
K+ channel database: a molecular specific information system for potassium channels
Glossary
- POLYAMINES
-
Long-chain aliphatic compounds that contain more than one amine group. Putrescine, spermine and spermidine are prime examples. Because of the positive charges on these molecules, polyamines bind electrostatically to proteins, DNA and RNA.
- RCK DOMAINS
-
(Regulator of K+ conductance domains). A ligand-binding domain found in many ligand-gated K+ channels; in MthK the ligand is thought to be nicotinamide adenine dinucleotide.
- MUTAGENESIS
-
Technique in which an alteration is made either at a specific site or randomly in a DNA molecule. Mutated DNA is then reintroduced into a cell and analysed with various techniques to determine which parts of a protein or nucleotide sequence are crucial for its function.
- SALT BRIDGE
-
Electrostatic interaction between oppositely charged amino-acid side chains in close proximity in a protein.
- RESTING POTENTIAL
-
The separation of positive and negative charges across the cell membrane results in the membrane potential. The resting potential is the membrane potential at which there is no net current flow across the cell membrane.
- TITRATABLE RESIDUE
-
An amino acid with a side chain that can bond and release protons within a physiological pH range. Seven of the twenty amino acids are titratable (pKa of the free amino acid is given in parenthesis; this can vary in the protein): aspartate (4.4), glutamate (4.4), histidine (6.5), cysteine (8.5), tyrosine (10), lysine (10) and arginine (12).
- SUBSTITUTED CYSTEINE ACCESSIBILITY METHOD
-
(SCAM). An approach to the characterization of channel and binding site structures that probes the environment of any residue by mutating it to cysteine and characterizing the reaction of the cysteine with sulphydryl reacting and coordinating reagents.
- SITE-DIRECTED SPIN LABELLING
-
(SDSL). In SDSL, a nitroxide side chain is introduced by cysteine substitution mutagenesis followed by modification of the unique sulphydryl group with a specific nitroxide reagent. Measurements of the spectral properties of the paramagnetic nitroxide probe with electron paramagnetic resonance (EPR) spectroscopy provide information on its environment in the protein.
- ELECTRON PARAMAGNETIC RESONANCE
-
(EPR). When an atom with an unpaired electron is placed in a magnetic field, the spin of the unpaired electron can align, either in the same direction or in the opposite direction. EPR is used to measure the absorption of microwave radiation that accompanies the transition between those two states.
- C-TYPE INACTIVATION
-
Two distinct molecular mechanisms for voltage-gated K+ channel inactivation have been described: N-type, which involves occlusion of the pore by an intracellular domain of the channel, and C-type, which involves a conformational change in the outer pore.
- TEMPERATURE FACTOR
-
(B-factor, Debye-Waller factor). A measure of atomic vibration as described by the spread of the electron density. A low B-factor indicates low atomic mobility.
- ENERGY WELLS
-
Discrete sites along the conduction pore of the channel, which are energetically favourable. These sites arise from a delicate balance between interactions with the channel atoms, water in the channel and other ions. Wells are separated by barriers, which hinder diffusion. When the energy wells are low in energy compared with the barriers, the residence time of ions at these positions is long.
- PHOSPHATIDYLINOSITOL-4,5-BISPHOSPHATE
-
(PtdIns(4,5)P2). An anionic phospholipid found at low concentrations in biological membranes. It acts as a membrane-delimited second messenger, regulating the activity of a number of transporters and channels.
- PDZ DOMAIN
-
A peptide-binding domain that is important for the organization of membrane proteins, particularly at cell–cell junctions, including synapses. They can bind to the carboxy termini of proteins, or can form dimers with other PDZ domains. PDZ domains are named after the proteins in which these sequence motifs were originally identified (PSD95, Discs-large, zona occludens-1).
- RUNDOWN (OR WASHOUT)
-
Decrease in channel activity over time. Loss of phosphorylation and decrease of the levels of PtdIns(4,5)P2 and ATP have been suggested to cause rundown, but other processes that are not yet understood might occur.
- PHOSDUCIN
-
A phosphoprotein that modulates the phototransduction cascade by interacting with the βγ-subunits of the retinal G-protein transducin.
- FLUORESCENCE RESONANCE ENERGY TRANSFER
-
(FRET). A spectroscopic technique that is based on the transfer of energy from the excited state of a donor moiety to an acceptor. The transfer efficiency depends on the distance between the donor and the acceptor. FRET is often used to estimate distances between macromolecular sites in the 20–100-Å range or to study interactions between macromolecules in vivo.
Rights and permissions
About this article
Cite this article
Bichet, D., Haass, F. & Jan, L. Merging functional studies with structures of inward-rectifier K+ channels. Nat Rev Neurosci 4, 957–967 (2003). https://doi.org/10.1038/nrn1244
Issue Date:
DOI: https://doi.org/10.1038/nrn1244
This article is cited by
-
New Structural insights into Kir channel gating from molecular simulations, HDX-MS and functional studies
Scientific Reports (2020)
-
Genetic causes of primary aldosteronism
Experimental & Molecular Medicine (2019)
-
Functional characterization of Kv11.1 (hERG) potassium channels split in the voltage-sensing domain
Pflügers Archiv - European Journal of Physiology (2018)
-
A synergistic blocking effect of Mg2+ and spermine on the inward rectifier K+ (Kir2.1) channel pore
Scientific Reports (2016)