アデニリルサイクラース活性化剤Gsalphaの結晶構造
R K Sunahara1, J J Tesmer, A G Gilman
1Department of Pharmacology, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75235-9041, USA.
まとめ
重要なシグナル伝達タンパク質であるGsalphaの結晶構造は,GTPgammaS.を用いて明らかにされました. Gialphaと比較してその構造の違いは,エフェクタ特異性と信号調節器との相互作用を説明します.
科学分野:
- 構造生物学 構造生物学とは
- 分子生物学は分子生物学である.
- バイオケミストリー バイオケミストリー
背景:
- Gサルファは,アデニリルサイクラスを活性化する重要なヘトロトリメリックGタンパク質アルファサブユニットです.
- これは,GTP結合タンパク質の家族に属し,ホルモンに依存した方法でエフェクター活動を調節します.
研究 の 目的:
- グアノシン5'-O-(3-チオートリフォスファート) (GTPgammaS) との複合体におけるGsalphaの結晶構造を決定する.
- Gsalpha.GTPgammaSとGialpha.GTPgammaSの構造を比較して,エフェクター特異性を理解する.
- GサルファとGタンパク質シグナル伝達 (RGS) のレギュレータとの相互作用の分子基礎を解明する.
主な方法:
- 2.5Aの解像度のX線結晶学.
- Gsalpha.GTPgammaSとGialpha.GTPgammaS複合体の構造比較について
- GsalphaとGialpha.の間の配列ホモロジーと構造的差異の分析.
主要な成果:
- Gsalpha.GTPgammaSの結晶構造が決定されました.
- エフェクター特異性は,高シーケンスホモロジーにもかかわらず,スイッチIIヘリックスとalpha3-beta5ループの結合表面の形によって主に決定されます.
- 構造的差異ではなく,配列の差異が,RGSタンパク質がGsalpha GTPaseの活性を刺激できない理由です.
- ベタガマ結合表面は保たれているが,カルボキシル末端ヘリックスとアルファ4-ベータ6ループの違いは受容体の特異性を媒介する可能性がある.
結論:
- Gsalphaの構造的な洞察は,Gタンパク質のシグナル伝達特異性を理解するための基礎を提供します.
- 特定の構造要素の違いがエフェクタとRGSの相互作用を左右し,保存された領域はベタガマサブユニット結合を媒介する.
- この研究は,Gsalphaが複雑な細胞シグナル伝達経路内で特定の機能をどのように達成するかを明らかにしています.
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関連する概念動画
G-protein Coupled Receptors
G-protein coupled receptors are ligand binding receptors that indirectly affect changes in the cell. The actual receptor is a single polypeptide that transverses the cell membrane seven times creating intracellular and extracellular loops. The extracellular loops create a ligand specific pocket which binds to neurotransmitters or hormones. The intracellular loops holds onto the G-protein.
GTPases and their Regulation
Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...
Large G-proteins, also known...
G-protein Coupled Receptors
G-protein coupled receptors are ligand binding receptors that indirectly affect changes in the cell. The actual receptor is a single polypeptide that transverses the cell membrane seven times creating intracellular and extracellular loops. The extracellular loops create a ligand specific pocket which binds to neurotransmitters or hormones. The intracellular loops holds onto the G-protein.
GTPases and their Regulation
Guanine nucleotide-binding proteins (G-proteins), also known as GTPases, are a superfamily of proteins that regulate many cellular processes, such as cell signaling, vesicular transport, and the regulation of cell shape and motility. Mutation or dysfunction of these proteins can lead to disease. There are around 40,000 known G-proteins that can broadly be classified into two groups ‒ small G-proteins consisting of a single domain and large multi-domain G-proteins.
Large G-proteins, also known...
Large G-proteins, also known...
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GPCRs Regulate Adenylyl Cylase Activity
Some GPCRs transmit signals through adenylyl cyclase (AC), a transmembrane enzyme. AC helps synthesize second messenger cyclic adenosine monophosphate (cAMP). AC catalyzes cyclization reaction and converts ATP to cAMP by releasing a pyrophosphate. The pyrophosphate is further hydrolyzed to phosphate by the enzyme pyrophosphatase, which drives cAMP synthesis to completion. However, cAMP is rapidly degraded to 5′ AMP by the enzymes phosphodiesterase (PDE), preventing overstimulation of cells.
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