大肠杆菌基因组为双链环状的DNA分子
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• 大肠杆菌及其他原核细胞就是以这种拟核形式在细 胞中执行着诸如复制、重组、转录、翻译以及复杂 的调节过程。
• 基因组全序列测定于1997年由Wisconsin大学的 Blattner等人完成。
DNA domains
• The DNA consists of 50-100 domains or loop. Each domain has supercoiling of different level. The E.coli chromosome as a whole is negatively supercoiled.
• The domains are wrapped by nonspecifical histone-like proteins such as HU and H-NS, so half of the supercoilings are constrained.
• RNA polymerase and mRNA molecules and site-specific DNA-binding proteins such as integration host factor (IHF) may be important in the organiBiblioteka Baiduation of the DNA domains.
The structures, functions and locations in gene map of 1400 genes have been confirmed.
• Nucleoid: no nucleic membrane, no nucleolus, no fixed configuration, simple structure
HU 两个9KD的不同亚基 40000个二体聚体
HLP1
17KD的亚基
20000个单体
P
3KD的亚基
未知
• 这些DNA结合蛋白，使E.coli 染色体DNA压缩成为 一个脚手架形结构，结构中心是多种DNA结合蛋 白，DNA双螺旋分子有许多位点与这些蛋白结合， 形成约100个小区，每个小区的DNA都是负超螺旋， 一个小区的DNA有两个端点被蛋白质固定，每个 小区相对独立。
Nucleoid
• 大肠杆菌基因组为双链环状的DNA分子，在细胞中 以紧密缠绕成的较致密的不规则小体形式存在于细 胞中，该小体称为拟核（nucleoid）,其上结合有类组 蛋白和少量RNA分子，并压缩形成一种脚手架形的 （scaffold）致密结构。
• 该区域DNA浓度高达30~50mg/ml。正常生长时， DNA保持持续复制。生长时，DNA持续复制，生长速 率最大时，每个细胞平均有基因组的两个拷贝。
• highly ordered DNA-protein complexes such as nucleosomes have not been detected.
Supercoiling of the genome
DNA-binding proteins
• H 两个28KD的相同亚基 30000个二聚体
• The ends of domains are constrained by binding to a structure which probably consists of proteins attached to part of the cell membrane.
• The loops are about 50-100kb in size.
• The DNA is made up of a number of discrete bodies called chromosomes.
• Each chromosome is a single linear molecule, which can be up to several centimeters long.
• Chromatin: a highly organized complex of DNA and protein （1︰1）
HU
• HU被称为类组蛋白(histone-like protein)。
• 在动物、植物细胞里，很长很长的DNA分子靠一 些叫做组蛋白(histones)的蛋白质来组织、压缩， 才能装进空间较小的细胞核。
• 在细菌细胞内，HU被认为起类似组蛋白的作用。 HU由两个相似的亚基构成，分别称为HU-和H U-。两个亚基各形成一个类似受臂的结构，将 双螺旋的DNA分子抱住。
D1 Prokaryotic chromosome structure
• The Escherichia coli chromosome • DNA domains
• DNA-binding proteins
The Escherichia coli chromosome
• A single closed-circular dsDNA molecule • Total length: 1300 µm • Molecular weight: 2.8*109D • Base pairs: 4.6 Mb • The number or genes : 3000-4000
D2 Chromatin structure
• Chromatin • Histones • Nucleosomes
Chromatin
• The total length of DNA in a eukaryotic cell depends on the species, but it can be thousands of times as much as in a prokaryotic genome.
• D1 prokaryotic chromosome structure • D2 chromatin structure • D3 eukaryotic chromosome structure • D4 genome complexity • D5 the flow of genetic information
• 基因组全序列测定于1997年由Wisconsin大学的 Blattner等人完成。
DNA domains
• The DNA consists of 50-100 domains or loop. Each domain has supercoiling of different level. The E.coli chromosome as a whole is negatively supercoiled.
• The domains are wrapped by nonspecifical histone-like proteins such as HU and H-NS, so half of the supercoilings are constrained.
• RNA polymerase and mRNA molecules and site-specific DNA-binding proteins such as integration host factor (IHF) may be important in the organiBiblioteka Baiduation of the DNA domains.
The structures, functions and locations in gene map of 1400 genes have been confirmed.
• Nucleoid: no nucleic membrane, no nucleolus, no fixed configuration, simple structure
HU 两个9KD的不同亚基 40000个二体聚体
HLP1
17KD的亚基
20000个单体
P
3KD的亚基
未知
• 这些DNA结合蛋白，使E.coli 染色体DNA压缩成为 一个脚手架形结构，结构中心是多种DNA结合蛋 白，DNA双螺旋分子有许多位点与这些蛋白结合， 形成约100个小区，每个小区的DNA都是负超螺旋， 一个小区的DNA有两个端点被蛋白质固定，每个 小区相对独立。
Nucleoid
• 大肠杆菌基因组为双链环状的DNA分子，在细胞中 以紧密缠绕成的较致密的不规则小体形式存在于细 胞中，该小体称为拟核（nucleoid）,其上结合有类组 蛋白和少量RNA分子，并压缩形成一种脚手架形的 （scaffold）致密结构。
• 该区域DNA浓度高达30~50mg/ml。正常生长时， DNA保持持续复制。生长时，DNA持续复制，生长速 率最大时，每个细胞平均有基因组的两个拷贝。
• highly ordered DNA-protein complexes such as nucleosomes have not been detected.
Supercoiling of the genome
DNA-binding proteins
• H 两个28KD的相同亚基 30000个二聚体
• The ends of domains are constrained by binding to a structure which probably consists of proteins attached to part of the cell membrane.
• The loops are about 50-100kb in size.
• The DNA is made up of a number of discrete bodies called chromosomes.
• Each chromosome is a single linear molecule, which can be up to several centimeters long.
• Chromatin: a highly organized complex of DNA and protein （1︰1）
HU
• HU被称为类组蛋白(histone-like protein)。
• 在动物、植物细胞里，很长很长的DNA分子靠一 些叫做组蛋白(histones)的蛋白质来组织、压缩， 才能装进空间较小的细胞核。
• 在细菌细胞内，HU被认为起类似组蛋白的作用。 HU由两个相似的亚基构成，分别称为HU-和H U-。两个亚基各形成一个类似受臂的结构，将 双螺旋的DNA分子抱住。
D1 Prokaryotic chromosome structure
• The Escherichia coli chromosome • DNA domains
• DNA-binding proteins
The Escherichia coli chromosome
• A single closed-circular dsDNA molecule • Total length: 1300 µm • Molecular weight: 2.8*109D • Base pairs: 4.6 Mb • The number or genes : 3000-4000
D2 Chromatin structure
• Chromatin • Histones • Nucleosomes
Chromatin
• The total length of DNA in a eukaryotic cell depends on the species, but it can be thousands of times as much as in a prokaryotic genome.
• D1 prokaryotic chromosome structure • D2 chromatin structure • D3 eukaryotic chromosome structure • D4 genome complexity • D5 the flow of genetic information