Abstract
The steep dependence of channel opening on membrane voltage allows voltage-dependent K+ channels to turn on almost like a switch. Opening is driven by the movement of gating charges that originate from arginine residues on helical S4 segments of the protein. Each S4 segment forms half of a 'voltage-sensor paddle' on the channel's outer perimeter. Here we show that the voltage-sensor paddles are positioned inside the membrane, near the intracellular surface, when the channel is closed, and that the paddles move a large distance across the membrane from inside to outside when the channel opens. KvAP channels were reconstituted into planar lipid membranes and studied using monoclonal Fab fragments, a voltage-sensor toxin, and avidin binding to tethered biotin. Our findings lead us to conclude that the voltage-sensor paddles operate somewhat like hydrophobic cations attached to levers, enabling the membrane electric field to open and close the pore.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Antibodies, Monoclonal / immunology
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Archaeal Proteins / chemistry
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Archaeal Proteins / immunology
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Archaeal Proteins / metabolism
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Avidin / metabolism
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Biotin / metabolism
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Desulfurococcaceae / chemistry
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Desulfurococcaceae / metabolism
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Hydrophobic and Hydrophilic Interactions
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Immunoglobulin Fab Fragments / immunology
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Ion Channel Gating*
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Models, Biological
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Models, Molecular
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Molecular Sequence Data
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Motion
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Potassium Channels, Voltage-Gated / antagonists & inhibitors
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Potassium Channels, Voltage-Gated / chemistry*
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Potassium Channels, Voltage-Gated / immunology
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Potassium Channels, Voltage-Gated / metabolism*
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Protein Structure, Tertiary
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Static Electricity
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Structure-Activity Relationship
Substances
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Antibodies, Monoclonal
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Archaeal Proteins
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Immunoglobulin Fab Fragments
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Potassium Channels, Voltage-Gated
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Avidin
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Biotin