2001 Fiscal Year Final Research Report Summary
Roles of water on the functions of ion channels
| Project/Area Number |
12670053
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General physiology
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| Research Institution | Okazaki Research Institutes |
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Principal Investigator |
KUKITA Fumio Okazaki Research Institutes National Institutes for Physiological Sciences, Research Associate, 生理学研究所, 助手 (40113427)
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| Project Period (FY) |
2000 – 2001
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| Keywords | ion channel / fluctuation in proteins / water / voltage-sensor / structure / squid giant axion / viscosity / osmotic pressure |
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| Research Abstract |
Ion channels has been generally thought to work in the lipid environment and then be regulated by the physical properties of lipid. However, they are controlled by the physical properties of aqueous solutions facing the ion channels but not by those of lipids. The rate of opening of Squid K^+ channels are controlled by the solution viscosity as that of Squid Na^+ channels. In a concentrated nonelectrolyte solutions, the time course of opening of Na^+ channels and K^+ channels was slowed mainly by way of a viscosity-dependent slowing of voltage-sensor movement.
Ion channels are pertinently designed to have an aqueous pore for ions to permeate thought the hydrophobic lipid bilayer. Therefore, a decrease in a water activity in the environment of channel pore has been thought to depress a channel pore opening. This is observed in the sodium channel but is not in all ionic channels, depending on the pore interior structure. Although opening of K^+ channel was also slowed by viscosity, a part of channels opened at the instant of a depolarizing voltage jump from -180 mV, as if pore is free from the control of voltage-sensor. The channel in this open state can close very slowly with the time constant larger by 50-fold on returning to -180 mV. These data suggested that volume of pore interior decreased when the channel was open. Even if the volume decreases, the wavy surface of pore interior might be smooth and narrow constrictions might disappear for ions to pass smoothly. Osmotic effects on the channel pore might suggest a pore interior structure which dose not parallel the conductance itself.
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Research Products
(8 results)
