タンパク質転位におけるSeCA ATPaseの2ヘリックス指の役割
Karl J Erlandson1, Stephanie B M Miller, Yunsun Nam
1Howard Hughes Medical Institute and Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, Massachusetts 02115, USA.
Nature
|October 17, 2008
まとめ
バクテリアにおけるSecAタンパク質の転位には,SecYチャンネルと相互作用する2ヘリックス指ドメインが含まれています. この領域における重要なチロシン残基は,ポロを介してポリペプチド鎖を移動させる上で極めて重要です.
科学分野:
- 分子生物学は分子生物学である.
- 細胞生物学 細胞生物学
- バイオケミストリー バイオケミストリー
背景:
- タンパク質が膜を横断して転移することは,プロカリオットとユーカリオットの両方の細胞機能にとって不可欠です.
- 細菌では,SecA ATPaseとSecY複合体は,分泌タンパク質の動きを促進する.
- SecAがSecYチャネルを通して基質を転位させる正確なメカニズムは,まだ完全に理解されていません.
研究 の 目的:
- タンパク質転位におけるSeCA双ヘリックス指領域の役割を調査する.
- 基板の移動中のSecAとSecYチャネルの相互作用を解明する.
- 転位に関与するSeCAの2ヘリックス指内の主要な残留物を特定するために.
主な方法:
- SecA-ポリペプチドの相互作用を調査するためのディスルフイドブリッジクロスリンク実験.
- SecAの2ヘリックス指領域のサイト指向型変異.
- エシェリキヤ大腸におけるタンパク質転位効率の分析.
主要な成果:
- ディスルファイド・ブリッジ・クロスリンクは,SecAの2ヘリックス指の先端にあるループがSecYチャネル入口にあるポリペプチド基板と相互作用することを確認した.
- 変異は,このループ内の特定のチロシン残基が効率的な転位に不可欠であることを明らかにしました.
- このチロシンを他の大量,水害性残留物に置き換えると,部分的に転位機能が回復し,基板結合または操作における役割を示唆しています.
結論:
- SecAの2ヘリックス指は,ポリペプチド鎖をSecYチャネルに移動させる直接的な役割を果たしています.
- SecAの2ヘリックス指にある重要なチロシン残基は,おそらく基板の主要な接触点として機能します.
- SecAによるタンパク質転位のこのメカニズムは,他のタンパク質転位ATPasesで観察されたものと類似しています.
関連する概念動画
01:19Translocation of Proteins into the Mitochondria
Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
01:37Energy to Drive Translocation
Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
Generally, polypeptides are unfolded by two distinct...
01:20Cotranslational Protein Translocation
Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
01:26Insertion of Single-pass Transmembrane Proteins in the RER
Integral membrane proteins are proteins adhered to the lipid bilayer of a cell organelle or membrane. They can be of two types: transmembrane integral proteins that span the lipid bilayer and monotopic proteins that are attached to either side of the membrane but do not pass through it.
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
Integral transmembrane proteins possess transmembrane and extra membrane domains. The transmembrane domains are primarily made of 20-25 hydrophobic amino acids arranged in a helical secondary confirmation. These...
01:27Post-translational Translocation of Proteins to the RER
A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
01:28Protein Translocation Machinery on the ER Membrane
The translocon complex situated on the ER membrane is the main gateway for the protein secretory pathway. It facilitates the transport of nascent peptides into the ER lumen and their insertion into the ER membrane.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.
Sec61 protein conducting channel
In eukaryotes, the translocon complex comprises a core heterotrimeric translocator channel called the Sec61 complex. This channel includes three transmembrane proteins, Sec61α, Sec61β, and Sec61γ, and is the largest subunit of the translocon complex.