Na+とK+を伝導するチャネルの原子構造
Ning Shi1, Sheng Ye, Amer Alam
1Department of Physiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9040, USA.
Nature
|February 10, 2006
まとめ
非選択性カチオンチャンネルであるNaKチャネルは,K+チャネルと異なるユニークな構造を持っています. その選択性フィルターアーキテクチャは,ナトリウム (Na +) とカリウム (K +) イオンの両方の伝導を可能にします.
科学分野:
- 構造生物学 構造生物学とは
- バイオフィジックス 生物物理学
- 分子生物学は分子生物学である.
背景:
- イオン選択性はイオンチャネルの基本的な性質です.
- K+チャネル選択性はよく知られていますが,他のカチオンチャネルにおける選択性の構造的根拠はほとんど不明です.
- テトラメリックカチオンチャネルは,共通の孔構造を共有しているが,イオン選択機構では異なっている.
研究 の 目的:
- バチルス・セレウスのNaKチャネルの結晶構造を決定する.
- NaKチャネルの非選択性の構造的根拠を解明する.
- NaKチャネル構造と既知のK+チャネルを比較する.
主な方法:
- X線結晶学により,Na+とK+結合状態のNaKチャネルの構造を取得する.
- 高解像度構造分析 (2.4 Å と 2.8 Å).
- 86Rb流量分析を用いた機能分析.
主要な成果:
- NaKチャネルは,KcsA K+チャネルと全体的な構造的な類似性を共有していますが,独特の選択性フィルターアーキテクチャを持っています.
- NaKチャネルの選択性フィルターは,2つのカチオン結合部位 (K+チャネル部位3と4に相当する) を保持しているが,2つの結合部位 (K+チャネル部位1と2に相当する) ではなく,ベスティビュールを持っている.
- 機能的測定は,NaKチャネルがNa+とK+イオンの両方を導いていることを確認しました.
結論:
- NaKチャネルの選択性フィルター構造は,K+チャネルとは大きく異なる.
- NaKチャネルのフィルター配列は,周期的なヌクレオチドゲートチャネルに似ており,その孔の潜在的な構造表現を示唆しています.
- 独特の構造は,チャネルがNa+とK+イオンの両方を伝導する能力を説明しています.
関連する概念動画
Ion 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...
Non-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.
The 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.
Voltage-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...
Non-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.
Voltage-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...


