Na,Kポンプへの細胞外アクセス:イオンチャネルに似た経路
D C Gadsby1, R F Rakowski, P De Weer
1Marine Biological Laboratory, Woods Hole, MA 02543.
まとめ
ナトリウム・カリウムポンプは,
科学分野:
- 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:
- Na,K-ATPase (ナトリウム-カリウムポンプ) は,細胞のイオングラデーションを維持するために不可欠です.
- 循環毎に3個のナトリウムイオンを運び出し,2個のカリウムイオンを運びます.
- イオン輸送中の電荷の移動は,ポンプの形状の変化と関連しています.
研究 の 目的:
- Na,K-ATPaseによるナトリウムイオン転位中の電荷移動の性質を調査する.
- ナトリウムイオンの放出と再結合の電圧依存度を測定する.
- パンプとイオンチャネルの機能的な類似性を理解するために.
主な方法:
- ボルテージ・クランプされた,内部で透析されたイカの巨大アクソンを利用した.
- カリウムの不在で,Na-Na交換経由で測定された一方的なナトリウム-22流出量.
- ポンプのナトリウム転位経路に焦点を当てました.
主要な成果:
- Na,K-ATPaseの活動は,電子中性であるが,電圧感受性を示した.
- 膜の負のポテンシャルが増えるにつれて,Na-Na交換の速度が加速した.
- 交換レートは,電圧で飽和するシグモイド曲線に従った.
結論:
- 外部ナトリウムイオンの放出と再結合は,電荷を移動させる主なステップです.
- 細胞外ナトリウムイオンは,ポンプ内の高フィールドチャネルを通って結合部位にアクセスします.
- Na,K-ATPase分子の一部は,イオンチャネルに類似して機能します.
関連する概念動画
Primary Active Transport
In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or electrochemical gradient. There are two types of active transport: primary active transport and secondary active transport. Primary active transport utilizes chemical energy from ATP to drive protein pumps that are embedded in the cell membrane. With energy from ATP, the pumps transport ions against their electrochemical gradients—a direction they...
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...
Primary Active Transport
In contrast to passive transport, active transport involves a substance being moved through membranes in a direction against its concentration or electrochemical gradient. There are two types of active transport: primary active transport and secondary active transport. Primary active transport utilizes chemical energy from ATP to drive protein pumps embedded in the cell membrane. With energy from ATP, the pumps transport ions against their electrochemical gradients—a direction they would not...
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.
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.


