導電形状に閉じ込められた半合成K+チャネルにおけるイオン選択性
Francis I Valiyaveetil1, Manuel Leonetti, Tom W Muir
1Laboratories of Molecular Neurobiology and Biophysics and Synthetic Protein Chemistry, Rockefeller University and Howard Hughes Medical Institute, 1230 York Avenue, New York, NY 10021, USA.
Science (New York, N.Y.)
|November 11, 2006
まとめ
研究者はイオン選択性を研究するために,カリウムチャネルを改変した. 変化したチャネルは,ナトリウムイオンを含む場合でも,そのカリウム伝導性構造を維持し,これらのチャネルがイオンを区別する方法に関する重要な洞察を明らかにしました.
科学分野:
- バイオケミストリー バイオケミストリー
- 分子生物学は分子生物学である.
- 構造生物学 構造生物学とは
背景:
- カリウムチャネルは細胞機能に不可欠であり,選択的にカリウムイオン (K+) が細胞膜を通過することを可能にします.
- これらのチャネル内の選択性フィルターは,K+とナトリウムイオン (Na+) を区別する責任を負う.
- 選択性フィルターの構造は,その中に結合したイオンの種類に基づいて適応することが知られている.
研究 の 目的:
- カリウムチャネルにおけるイオン選択性の構造的基礎を調査する.
- チャンネルの組成を変更すると,K+とNa+イオンを区別する能力に影響するかどうかを判断する.
- チャンネル選択性の維持におけるイオン競争の役割を明らかにする.
主な方法:
- サイト・ディレクテッド・ミュータゲネシスは,アラニンのd-エナティオマーを組み込んだ改変したカリウムチャネルを合成するために使用されました.
- 修正されたチャネルの高解像度構造を決定するために,X線結晶学を用いた.
- イオン伝導測定は,異なる条件下で,K+とNa+に対するチャネルの浸透性を評価するために実施されました.
主要な成果:
- 選択性フィルターに改変されたアミノ酸を入れた合成されたカリウムチャネルは,Na+と低K+濃度の存在でもK+伝導形状を維持した.
- 改造されたチャネルは,K+の不在でNa+伝導性を示した.
- Na+伝導はK+の存在で阻害され,フィルターの結合部位への競争を示した.
結論:
- カリウムチャネルのフィルター構造の異なるイオンへの適応性は,その選択性にとって根本的なものです.
- この発見は,選択性フィルターの機能的整合性を維持する上で,イオン競争が果たす重要な役割を強調しています.
- この研究は,生物学的イオンチャネルにおけるイオン選択性のメカニズムに関する新しい構造的および機能的な洞察を提供します.
関連する概念動画
01:19Ion Channels
The movement of ions like sodium, potassium, and calcium into and out of the cell is essential to maintain the electrochemical gradient in living cells. The ion channels—a class of membrane transport proteins—help maintain this ionic gradient for the smooth functioning of physiological activities such as maintaining cell size and volume, conducting nerve impulses, and gas and nutrient exchange.
Ion channels are specialized integral membrane proteins on the plasma membrane that allow specific...
Ion channels are specialized integral membrane proteins on the plasma membrane that allow specific...
01:24Non-gated Ion Channels
Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
01:19The Role of Ion Channels in Neuronal Computation
A postsynaptic neuron usually receives numerous impulses from several other presynaptic neurons. The axon hillock of the postsynaptic neuron integrates all these signals and determines the likelihood of firing an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
Sometimes a single EPSP is strong enough to induce an action potential in the postsynaptic neuron. However, multiple presynaptic inputs must often create EPSPs around the same time for the postsynaptic neuron to be sufficiently depolarized to fire an action potential.
01:26Voltage-gated Ion Channels
Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
01:24Non-gated Ion Channels
Ion channels are specialized proteins on the plasma membrane that allow charged ions to pass down their electrochemical gradient. Their main function is to maintain the membrane potential which is critical for cell viability. These channels are either gated or non-gated and can transport more than a thousand ions within milliseconds for the cellular event to occur.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
Compared to the gated ion channels, the non-gated channels, also known as leakage or passive channels, have no gating mechanism.
01:26Voltage-gated Ion Channels
Voltage-gated ion channels are transmembrane proteins that open and close in response to changes in the membrane potential. They are present on the membranes of all electrically excitable cells such as neurons, heart, and muscle cells.
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...
Generally, all voltage-gated ion channels have a 'voltage-sensing domain' that spans the lipid bilayer. The charged residues in the sensor move in response to the membrane potential changes that open the channel allowing ions movement. There are several types of...