Membrane Insertion of a Potassium-Channel Voltage Sensor

Hessa, Tara; White, Stephen H.; Heijne, Gunnar von

doi:10.1126/science.1109176

Cited by 175 publications

(233 citation statements)

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“…Two explanations for the Hessa et al (19) result are possible. One is that an inserted S4 helix associates with some other ER protein, thus shielding it from the lipid bilayer by salt-bridge formation or some kind of canaliculi.…”

mentioning

confidence: 90%

“…The smooth particle MD simulation of a model S4 voltage-sensor peptide (GGPG-LGLFRLVRLLRFLRILLII-GPGG) in a palmitoyloleoylphosphatidylcholine bilayer. This model was chosen because it is the one studied by Hessa et al (19). The simulation was carried out to understand the physical basis for the stable insertion of S4 across the ER by the translocon.…”

Section: Methodsmentioning

confidence: 99%

“…The values of ⌬G AA app were unfavorable in the center position, but became much less so as the residues were moved toward either of the H-segment ends. From the base biological scale and measurements of the position dependence of ⌬G Arg app and ⌬G Gly app , Hessa et al (19) were able to compute with remarkable accuracy the ⌬G app values observed for S4 and S4mut. The close agreement of the computed and observed free energy values indicates that position-adjusted additivity prevails in the insertion of S4 and that shielding of S4 by other ER proteins need not be invoked to explain the observed values of ⌬G app .…”

mentioning

confidence: 99%

“…Specifically, the S4-model helix used in the Hessa et al (19) experiments, GGPG-LGLFR LVR LLRFLR ILLII-GPGG, was inserted across a lipid bilayer comprised of palmitoyloleoylphosphatidylcholine. The simulation reveals a stabilizing hydrogen-bonded network of water and lipid phosphates around the arginines that reduces the effective thickness of the bilayer hydrocarbon core to Ϸ10 Å in the vicinity of the helix.…”

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confidence: 99%

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Interface connections of a transmembrane voltage sensor

Freites

Tobias

Heijne

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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sensors to lipid is contrary to the classical expectation that the dielectric contrast between the membrane hydrocarbon core and water presents an insurmountable energetic penalty to burial of electric charges. Nevertheless, recent experiments have shown that a helix with the sequence of KvAP S4 can be inserted across the endoplasmic reticulum membrane. To reconcile this result with the classical energetics argument, we have carried out a molecular dynamics simulation of an isolated TM S4 helix in a lipid bilayer. The simulation reveals a stabilizing hydrogen-bonded network of water and lipid phosphates around the arginines that reduces the effective thickness of the bilayer hydrocarbon core to Ϸ10 Å in the vicinity of the helix. It suggests that bilayer phospholipids can adapt locally to strongly perturbing protein elements, causing the phospholipids to become a structural extension of the protein.voltage-gated potassium channels ͉ lipid bilayer structure ͉ membrane electrostatics ͉ molecular dynamics simulation ͉ membrane proteins V oltage-sensitive ion channels (reviewed in ref. 1), which probably exist in all life forms (2), control the flow ionic currents down transmembrane (TM) electrochemical gradients in response to changes in membrane potential. They do this by opening and closing in response to changes in TM potential as a result of the motion of voltage-sensor domains (3). Voltagegated potassium (Kv) channels, perhaps the most intensely studied family of voltage-sensitive channels, are typically homotetramers assembled from monomers that have six TM helices (S1-S6) with a pore domain between S5 and S6. The principal voltage-sensing component is the S4 helix. Although rich in hydrophobic residues, it includes four or more positively charged amino acids, most commonly arginine, that cause S4 to respond to changes in membrane potential.The mechanistic details of the S4 response in Kv channels is a matter of considerable debate (4-8). The focus of the discussion is the so-called paddle model (9), which derives from the high-resolution structure (10) of the KvAP K ϩ channel from the archaebacterium Aeropyrum pernix (11), and more recently the structure of a mammalian voltage-dependent K ϩ channel (12, 13). This model posits that the four voltage paddles of the homotetramer, comprised of part of S3 (S3b) and S4, move within the membrane bilayer in response to TM voltage changes. The alternative view is that S4 moves inside water-filled canaliculi hidden from the bilayer by other parts of the channel protein (14). Although experimental studies show that synthetic peptides related to the S4 voltage sensor readily adopt surfacebound configurations with model membranes (15, 16), a TM configuration is contrary to the classical expectation that the dielectric contrast between the membrane hydrocarbon core and water presents an insurmountable energetic penalty to burial of electric charges (17,18).A key question is thus whether an isolated S4 segment can exist as a TM helix in the absence of the rest of the protei...

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confidence: 90%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Interface connections of a transmembrane voltage sensor

Freites

Tobias

Heijne

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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“…Hessa et al (31) evaluated the membrane-insertion potential of S4 from KvAP (a K v channel from Aeropyrum pernix) by measuring the apparent free energy of the translocon-mediated integration of S4 into the endoplasmic reticulum membrane. To confirm that Shaker and KAT1 S4 lack membrane-insertion properties, we used the same experimental system (31).…”

Section: Membrane Insertion Efficiencies Of Different Combinations Ofmentioning

confidence: 99%

Contribution of hydrophobic and electrostatic interactions to the membrane integration of the Shaker K ⁺ channel voltage sensor domain

Zhang

Sato

Hessa

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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Membrane-embedded voltage-sensor domains in voltage-dependent potassium channels (K v channels) contain an impressive number of charged residues. How can such highly charged protein domains be efficiently inserted into biological membranes? In the plant Kv channel KAT1, the S2, S3, and S4 transmembrane helices insert cooperatively, because the S3, S4, and S3-S4 segments do not have any membrane insertion ability by themselves. Here we show that, in the Drosophila Shaker Kv channel, which has a more hydrophobic S3 helix than KAT1, S3 can both insert into the membrane by itself and mediate the insertion of the S3-S4 segment in the absence of S2. An engineered KAT1 S3-S4 segment in which the hydrophobicity of S3 was increased or where S3 was replaced by Shaker S3 behaves as Shaker S3-S4. Electrostatic interactions among charged residues in S2, S3, and S4, including the salt bridges between E283 or E293 in S2 and R368 in S4, are required for fully efficient membrane insertion of the Shaker voltage-sensor domain. These results suggest that cooperative insertion of the voltage-sensor transmembrane helices is a property common to Kv channels and that the degree of cooperativity depends on a balance between electrostatic and hydrophobic forces.charged residue ͉ Kv channel ͉ salt bridge ͉ translocation

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Automated Large‐Scale Purification of a Recombinant G‐Protein‐Coupled Neurotensin Receptor

White

Grisshammer

2007

CP Protein Science

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Structure determination of G-protein-coupled receptors and other applications, such as nuclear magnetic resonance (NMR) studies, require milligram quantities of purified, functional receptor protein on a regular basis. This unit presents a step-by-step procedure for the automated two-column purification at the 10-milligram scale of a G protein-coupled receptor for neurotensin, expressed in functional form in Escherichia coli.

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Membrane Insertion of a Potassium-Channel Voltage Sensor

Cited by 175 publications

References 6 publications

Interface connections of a transmembrane voltage sensor

Interface connections of a transmembrane voltage sensor

Contribution of hydrophobic and electrostatic interactions to the membrane integration of the Shaker K ⁺ channel voltage sensor domain

Automated Large‐Scale Purification of a Recombinant G‐Protein‐Coupled Neurotensin Receptor

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Membrane Insertion of a Potassium-Channel Voltage Sensor

Cited by 175 publications

References 6 publications

Interface connections of a transmembrane voltage sensor

Interface connections of a transmembrane voltage sensor

Contribution of hydrophobic and electrostatic interactions to the membrane integration of the Shaker K + channel voltage sensor domain

Automated Large‐Scale Purification of a Recombinant G‐Protein‐Coupled Neurotensin Receptor

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Contribution of hydrophobic and electrostatic interactions to the membrane integration of the Shaker K ⁺ channel voltage sensor domain