ATPの水解へのキネシンステップの結合
W Hua1, E C Young, M L Fleming
1Biophysics and Structural Biology Graduate Program, Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254, USA.
Nature
|July 24, 1997
まとめ
研究者はキネシンの運動運動を定量化し,1つのATP分子がマイクロチューブルに沿って8nmのステップを動かすことを発見しました. この1ATPから8nmの結合は,様々なATP濃度において一貫しており,キネシンを明らかにしています.
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.
- 細胞生物学 細胞生物学
背景:
- キネシンなどのATP駆動モータータンパク質は,細胞内輸送に不可欠です.
- キネシンの正確な機械的ステップとエネルギー結合を理解することは,その機能を明らかにするために不可欠です.
- 以前の研究では,キネシンのステップサイズ (5-8 nm) が異なることが報告され,分析はブラウンの運動と急速なATP周回によって複雑になりました.
研究 の 目的:
- 単一のATP分子で動かすキネシン運動のステップサイズを正確に定量化するために.
- ATPの水解とキネシンの機械的移動の関係を解明するために.
- 観察された結合が,異なるATP濃度において一貫しているかどうかを判断する.
主な方法:
- 超低位置漂移 (<39 pms[-1]) を有する高度な光顕微鏡を用いた.
- 非常に低いATP濃度 (150nM) でゆっくり動く単一のキネシン分子が観測され,時間的な出来事を分離する.
- ステップサイズとATPカップリングを決定するために,未解決の動きを考慮した統計ベースの分析方法を適用しました.
主要な成果:
- キネシンは,単一のATP水解イベントが8.12 nmのステップ距離と結合し,マイクロチューブルのプロトフィラメントの格子間隔に匹敵する基本的な酵素サイクルを示しています.
- 他のステップ距離の動きや複雑なATP対ステップ結合比 (例えば,ステップあたり2ATP) は除外された.
- ATP消費率とステップアップ率の比率は,幅広い範囲のATP濃度において不変である.
結論:
- キネシンの基本的ステップサイズは8nmで,直接1つのATP分子の水解と結合しています.
- この1 ATP:8 nmの結合メカニズムは,低濃度から高濃度のATPに適用できるキネシンの酵素サイクルの一般的な特徴です.
- この発見は,分子レベルでのキネシンの機械的機能の明確な定量的な理解を提供します.
関連する概念動画
01:08Hydrolysis of ATP
The bonds of adenosine triphosphate (ATP) can be broken through the addition of water, releasing one or two phosphate groups in an exergonic process called hydrolysis. This reaction liberates the energy in the bonds for use in the cell—for instance, to synthesize proteins from amino acids.
If one phosphate group is removed, a molecule of ADP—adenosine diphosphate—remains, along with inorganic phosphate. ADP can be further hydrolyzed to AMP—adenosine monophosphate—by the removal of a second...
If one phosphate group is removed, a molecule of ADP—adenosine diphosphate—remains, along with inorganic phosphate. ADP can be further hydrolyzed to AMP—adenosine monophosphate—by the removal of a second...
01:32Chemiosmosis
Oxidative phosphorylation is a highly efficient process that generates large amounts of adenosine triphosphate (ATP), the basic unit of energy that drives many cellular processes. Oxidative phosphorylation involves two processes— the electron transport chain and chemiosmosis.
Electron Transport Chain
The electron transport chain involves a series of protein complexes on the inner mitochondrial membrane that undergo a series of redox reactions. At the end of this chain, the electrons reduce...
Electron Transport Chain
The electron transport chain involves a series of protein complexes on the inner mitochondrial membrane that undergo a series of redox reactions. At the end of this chain, the electrons reduce...
01:08Hydrolysis of ATP
The bonds of adenosine triphosphate (ATP) can be broken through the addition of water, releasing one or two phosphate groups in an exergonic process called hydrolysis. This reaction liberates the energy in the bonds for use in the cell—for instance, to synthesize proteins from amino acids.
If one phosphate group is removed, a molecule of ADP—adenosine diphosphate—remains, along with inorganic phosphate. ADP can be further hydrolyzed to AMP—adenosine monophosphate—by the removal of a second...
If one phosphate group is removed, a molecule of ADP—adenosine diphosphate—remains, along with inorganic phosphate. ADP can be further hydrolyzed to AMP—adenosine monophosphate—by the removal of a second...
01:48ATP Synthase: Mechanism
In animals, the mitochondrial F1F0 ATP synthase is the key protein that synthesizes ATP molecules through a complex catalytic mechanism. While the nuclear genome encodes the majority of ATP synthase subunits, the mitochondrial genome encodes some of the enzyme's most critical components. The formation of this multi-subunit enzyme is a complex multi-step process regulated at the level of transcription, translation, and assembly. Defects in one or more of these steps can result in decreased ATP...
01:31ATP Energy Storage and Release
ATP is a highly unstable molecule. Unless quickly used to perform work, ATP spontaneously dissociates into ADP and inorganic phosphate (Pi), and the free energy released during this process is lost as heat. The energy released by ATP hydrolysis is used to perform work inside the cell and depends on a strategy called energy coupling. Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions, allowing them to proceed.
One example of energy coupling using ATP involves a...
One example of energy coupling using ATP involves a...
01:31ATP Energy Storage and Release
ATP is a highly unstable molecule. Unless quickly used to perform work, ATP spontaneously dissociates into ADP and inorganic phosphate (Pi), and the free energy released during this process is lost as heat. The energy released by ATP hydrolysis is used to perform work inside the cell and depends on a strategy called energy coupling. Cells couple the exergonic reaction of ATP hydrolysis with endergonic reactions, allowing them to proceed.
One example of energy coupling using ATP involves a...
One example of energy coupling using ATP involves a...