通过TRAPP膜结合复合体激活Rab Ypt1p的结构基础
Yiying Cai1, Harvey F Chin, Darina Lazarova
1Department of Cell Biology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA.
Cell
|July 1, 2008
概括
TRAPPI复合体通过稳定其核酸结合口袋来激活Ypt1p,这是膜融合前的关键步骤. 这种对Rab GTPase激活的结构洞察力为了解膜结合提供了一个分子框架.
科学领域:
- 分子细胞生物学 分子细胞生物学
- 膜贩卖 膜贩卖 膜贩卖
- 结构生物学 结构生物学
背景情况:
- 多重分子膜结合复合体,TRAPPI和TRAPPII,对于细胞膜融合事件至关重要.
- 这些复合体共享子单元,并参与激活Rab GTPases,如Ypt1p,这调节了膜动力学.
研究的目的:
- 阐明TRAPPI复合物激活Rab GTPase Ypt1p的分子机制.
- 介绍TRAPPI-Ypt1p相互作用在膜融合之前的结构基础.
主要方法:
- 确定了与Ypt1p.p.复合的异构米TRAPPI组件的结构.
- 利用结构分析来识别特定的子单元相互作用及其在Ypt1p激活中的功能作用.
主要成果:
- TRAPPI通过将其核酸结合口袋稳定到开放的形状中来激活Ypt1p,从而促进核酸交换.
- Bet3p,Bet5p和Trs23p与Ypt1p直接相互作用,Bet3p的C终端重塑了口袋.
- 在没有直接相互作用的情况下,Trs31p以全质调节TRAPPI-Ypt1p接口.
结论:
- 这些发现为了解膜结合中的Rab GTPase激活提供了分子框架.
- 由TRAPPI激活Ypt1p的拟议机制很可能保留在相关的TRAPPII综合体中.
- 对TRAPPI-Ypt1p复合体形成的结构洞察力揭示了膜融合之前的关键事件.
相关概念视频
Rab Cascades
Rab GTPases act in a regulated cascade during membrane fusion, helping the lipid bilayers mix. The Rab family of proteins are active when bound to GTP, and inactive when bound to GDP. Hence, they act as guanine nucleotide-dependent molecular switches. Rab-GTP recognizes and binds to long or short-range tethering proteins to capture the target vesicle. These tethers coordinate with SNAREs on the vesicle and the target membrane to assemble the trans SNARE complex that locks the mixing bilayers.
Rab Proteins
Rab proteins constitute the largest family of monomeric GTPases, of which 70 members are present in humans. Rab proteins and their effectors regulate consecutive stages of vesicle transport such as vesicle transport, docking, and fusion to the correct recipient membrane.
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Rab proteins switch between a cytosolic, GDP-bound inactive state and a membrane-anchored, GTP-bound active state. By themselves, Rabs show slow rates of GDP/GTP exchange and GTP hydrolysis. Thus, Rab proteins are considered...
Cotranslational Protein Translocation
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Sec61 channel partners for cotranslational translocation
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Sec61 channel partners for cotranslational translocation
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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
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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.
Tail-anchoring of Proteins in the ER Membrane
Tail-anchored, or TA, proteins are estimated to make up to 3-5% of membrane proteins found in the eukaryotic cell. Such proteins have a single transmembrane domain located approximately 30 amino acid residues upstream from the C-terminal end. As a result, the signal recognition particle (SRP) cannot guide a TA protein to the ER membrane for cotranslational insertion. Hence, they are integrated into the ER membrane post-translationally using their C-terminal end as the anchor. TA proteins...
SNAREs and Membrane Fusion
Once a transport vesicle has recognized its target organelle, the vesicular membrane needs to fuse with the target membrane to unload the cargo. Transmembrane proteins called SNAREs present on organelle membranes and their vesicles, mediate vesicle fusion.
SNAREs exist in pairs that symmetrically interact and catalyze the fusion of the lipid bilayers in vesicle and target organelle. v-SNARE in the vesicle membrane are single polypeptide chains that bind to a complementary t-SNARE, composed of 2...
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