L型Ca2+チャネルにおけるCa2+選択性とイオン浸透性の分子決定因子
J Yang1, P T Ellinor, W A Sather
1Department of Molecular and Cellular Physiology, Beckman Center, Stanford University Medical Center, California 94305.
Nature
|November 11, 1993
まとめ
この研究は,カルシウムチャネル内の4つの重要なグルタミン酸残留物が,高親和性カルシウムイオン結合に不可欠であることを明らかにしています. 改変により,これらの残留物は,カルシウム選択性および浸透性にとって極めて重要であり,細胞信号伝達に影響を及ぼすことが示されています.
科学分野:
- 分子生物学は分子生物学である.
- バイオフィジックス 生物物理学
- 細胞生理学 細胞生理学
背景:
- 電圧誘導カルシウムチャネルは,様々な細胞反応に不可欠な細胞カルシウム流入を制御します.
- これらのチャネルは,ナトリウム (Na+) とカリウム (K+) のイオンよりも,カルシウムイオン (Ca2+) の選択性を示す.
- チャネル孔内の4つの保存されたグルタミン酸残基は,Ca2+結合を媒介すると仮定されています.
研究 の 目的:
- Ca2+チャネルポールの4つの保存されたグルタミン酸残留物の役割を体系的に調査する.
- 高親和性Ca2+結合とイオン選択性に対する各グルタミン酸の寄与を決定する.
- 電圧ゲートチャネルを通じたCa2+の浸透の支配的なモデルを精錬する.
主な方法:
- サイト・ディレクテッド・ミュータゲネシスにより,4つの重要なグルタミン酸位置のそれぞれに単一のアミノ酸置換を生成する.
- 変異がCa2+とCd2+結合に及ぼす影響を評価するための電気生理学的記録.
- イオン結合親和性に対する個々の残留物の貢献を評価するためにCa2+ブロックの分析.
主要な成果:
- 4つのグルタミン酸残留物は,Ca2+とCd2+の高親和結合に関与していることが判明しました.
- 各グルタミン酸は,イオン結合に明確に寄与し,リピートIIIの残基が最も重要な効果を示しています.
- 特定のグルタミン酸部位におけるライシンへの変異は,マイクロモラーCa2+ブロックを廃止し,その重要な役割を示した.
結論:
- Ca2+の浸透に関する現在のモデルは,4つのグルタミン酸残基の近くにある2つのCa2+イオンの結合を含むように変更する必要があります.
- これらのグルタミン酸の機能的不平等は,単一のファイルで移動する複数のCa2+イオンの同時結合を促進する可能性があります.
- イオン間のイオン競争とCa2+イオン間の静電抵抗は,急速なチャネル流速に寄与する可能性があります.
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