一种双功能细菌蛋白质将GDI位移与Rab1激活联系起来
Matthias P Machner1, Ralph R Isberg
1Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 02111, USA.
概括
军团菌蛋白SidM既作为瓜核酸交换因子 (GEF),又作为Rab1.1的GDI移位因子 (GDF). 这种双重活动对于在宿主细胞感染期间将Rab1招募到细菌真空中至关重要.
科学领域:
- 细胞生物学 细胞生物学
- 微生物学 微生物学
- 分子生物学分子生物学
背景情况:
- 拉布瓜诺辛三酸酶 (GTPases) 是真核细胞中囊泡贩运的关键调节者.
- 不活跃的Rab GTPases被GDP分离抑制剂 (GDI) 在细胞质中隔离.
- 通过特定因素取代GDI被认为是通过关氨酸核酸交换因子 (GEFs) 激活Rab GTPase的必要条件.
研究的目的:
- 为了研究莱吉欧内拉肺炎 SidM 蛋白质的功能.
- 为了确定SidM是否具有GDI移位因子 (GDF) 活动.
- 阐明SidM在宿主细胞感染期间的Rab1招募中的作用.
主要方法:
- 在试管测试中使用纯化的SidM和Rab1.1.进行了测试.
- 脂质体结合测试以评估膜关联.
- 分析Rab1对宿主细胞中含有军菌的真空体的招募.
主要成果:
- 赛德姆展示了双重活动,同时作为一个GEF和一个GDF的Rab1.
- 由SidM从GDI释放的Rab1被插入到脂质体膜中.
- 赛德姆的GDF活动对于将Rab1招募到含有军团菌的真空中至关重要.
结论:
- 一个单一的蛋白质,SidM,可以拥有GEF和GDF活动.
- 赛德姆的GDF功能对于协调从GDI绑定池中的Rab1招聘至关重要.
- 这项研究揭示了一种在细菌病变过程中调节Rab GTPase局部化的新机制.
相关概念视频
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.
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...
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...
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.
Small GTPases - Ras and Rho
Ras and Rho are small monomeric GTPases that act downstream of receptor tyrosine kinase (RTK) and regulate various cellular processes. These GTPases switch between active and inactive states by binding to guanine nucleotides.
Three regulatory proteins control their activity:
Three regulatory proteins control their activity:
Activation and Inactivation of G Proteins
Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...
IP3/DAG Signaling Pathway
Membrane lipids such as phosphatidylinositol (PI) are precursors for several membrane-bound and soluble second messengers. Specific kinases phosphorylate PI and produce phosphorylated inositol phospholipids. One such inositol phospholipids are the phosphatidylinositol-4,5 bisphosphate [PI(4,5)P2], present in the inner half of the lipid bilayer. Upon ligand binding, GPCR stimulates Gq proteins to turn on phospholipase Cꞵ. Activated phospholipase Cꞵ cleaves PI(4,5)P2 and produces two-second...
Coat Assembly and GTPases
Vesicles incorporate different coat protein subunits in different cell locations, which changes the properties of the coat, such as the shape and geometry of the transport vesicles. Thus, vesicle coat proteins also play a significant role in cargo selection.
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...
Coat assembly depends on the local availability of phosphatidylinositol phosphates or PIPs and GTP-binding proteins. Adaptor proteins, which link the coat proteins to the membrane, bind to these PIPs and play a crucial role in controlling...


