晶体结构解释了两种大肠杆菌体的功能性质
S W Cowan1, T Schirmer, G Rummel
1Department of Structural Biology, University of Basel, Switzerland.
Nature
|August 27, 1992
概括
促进分子扩散的细菌外膜毛孔,形成具有β-桶结构的trimers. 它们的孔隙收缩,受到带电环的影响,决定了离子选择性,并解释了突变效应.
科学领域:
- 结构生物学是结构生物学.
- 微生物学 微生物学
- 生物物理学的生物物理.
背景情况:
- 蛋白是格拉姆阴性细菌中必不可少的外膜蛋白.
- 它们形成水性通道,促进小水友分子的运输.
- 了解毛孔结构-功能关系对于理解细菌生理学至关重要.
研究的目的:
- 阐明波林功能背后的分子机制.
- 解释蛋白通道中离子选择性的结构基础.
- 为了将结构发现与已知的功能特征和突变相关联.
主要方法:
- 使用X射线晶体学来确定矩阵和的结构.
- 对16个链的反平行β桶架构的分析.
- 研究内部循环在通道收窄和离子选择性中的作用.
主要成果:
- 晶体结构揭示出波林是相同子单元的三元体.
- 每个子单元都有一个16条链的β-桶,形成一个通道.
- 一个长的内部循环产生了收缩,电荷分布控制了离子选择性.
结论:
- 确定的结构为蛋白的功能提供了分子基础.
- 结构洞察力解释了观察到的离子选择性和突变的影响.
- 这项工作增强了对跨越格拉姆阴性细菌外膜的传输的理解.
相关概念视频
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
01:12Porin Insertion in the Outer Mitochondrial Membrane
Porins are beta-barrel proteins translocated to the mitochondrial outer membrane through the TOM complex into the intermembrane space. Porin precursors bind TIM chaperones within the intermembrane space and are guided to the Sorting and Assembly Machinery complex or SAM complex on the outer mitochondrial membrane.
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...
01:25Aquaporins
Aquaporins or AQPs are a family of integral membrane proteins whose primary function is to transport water, while some called aquaglyceroporins also transport glycerol. In addition, aquaporins have also been suspected to be involved in transporting volatile substances, such as carbon dioxide and ammonia, across membranes. Such AQPs that act as gas channels are often highly expressed in cells involved in the gaseous exchange, such as red blood cells, epithelial cells, and pulmonary capillaries.
01:09Multi-pass Transmembrane Proteins and β-barrels
In multi-pass transmembrane proteins, the polypeptide chain crosses the membrane more than once. The transmembrane polypeptide chain either forms an α-helix or β-strand structure. α-Helix containing multi-pass transmembrane proteins are ubiquitous, whereas β-strand containing ones are mainly found in gram-negative bacteria, mitochondria, and chloroplasts.
α-Helix containing multi-pass transmembrane proteins
Multi-pass transmembrane proteins such as G-protein-linked receptors (GPCRs) and...
α-Helix containing multi-pass transmembrane proteins
Multi-pass transmembrane proteins such as G-protein-linked receptors (GPCRs) and...
01:21Structure of Porins
Mitochondria, chloroplasts, and gram-negative bacteria have transmembrane, beta-barrel proteins called porins to mediate the free diffusion of ions and metabolites across the membrane. Mitochondrial porin precursors contain conserved amino acid sequences called beta signals at their C-terminal. Beta signals have a motif of PoXGXXHyXHy (Po-Polar, X-Any amino acid, G-Glycine, Hy-LargeHydrophobic), which are crucial for precursor recognition to initiate precursor assembly. Beta-barrel precursors...
01:17Pore Transport and Ion-Pair Transport
Pore transport and ion-pair formation are critical mechanisms for the absorption and distribution of drugs in the body.
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...
Pore transport, also known as convective transport, is a process where small molecules like urea, water, and sugars rapidly cross cell membranes as though there were channels or pores in the membrane. Although direct microscopic evidence is limited but the concept of pores or channels is widely accepted based on physiological evidence. Despite the lack of direct microscopic...