关氨酸核酸交换因子人类Mss4的结构及其Rab交互表面的识别
1Howard Hughes Medical Institute, Department of Chemistry, Harvard University, Cambridge, Massachusetts 02138, USA.
Nature
|August 31, 1995
概括
人类Mss4 (hMss4),一种瓜核酸交换因子 (GEF),具有确定的三级结构. 这种结构揭示了它的活性部位涉及到一个Zn2+结合区域和一个邻近的循环,这对Rab蛋白调节至关重要.
科学领域:
- 生物化学 生物化学
- 结构生物学 结构生物学
- 分子细胞生物学 分子细胞生物学
背景情况:
- 关核酸交换因子 (GEFs) 是Ras GTPases的关键调节者,控制GDP/GTP交换和下游信号.
- 拉斯超级家族蛋白质的Sec4/Ypt1/Rab分支在囊泡运输中发挥着至关重要的作用.
- 哺乳动物抑制Sec4 (Mss4) 是一种GEF,用于Rab蛋白的特定子集.
研究的目的:
- 确定人类Mss4 (hMss4) 的三级结构,这是首个同类GEF结构.
- 阐明Mss4的GEF活动和Rab-binding相互作用的结构基础.
主要方法:
- 采用多维核磁共振 (NMR) 光谱学来确定hMss4.4的三级结构.
- 化学转移干扰实验和局部定向突变发生被用来绘制Rab-binding表面和活性部位.
主要成果:
- 建立了GEF蛋白质hMss4的第一个三级结构,揭示了一个中央的β-片,旁边有较小的片.
- 发现hMss4通过四种半氨酸残留物 (Cys 23, 26, 94, 97) 结合Zn2+离子.
- 划定了Rab结合表面和活性部位,包括Zn2+结合区域和相邻的循环.
结论:
- 确定hMss4的结构为Rab蛋白调节中的GEF活性机制提供了关键的见解.
- 了解Zn2+结合点和周围环路的结构和功能相互作用,对于理解Mss4在囊泡运输中的作用至关重要.
相关概念视频
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...
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...
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...


