细胞生物学_cytoskeleton
单词
filament 丝
treadmill 踏车
nucleation 核聚
elongation 扩展
steady state 稳态
critical concentration 关键浓度
treadmilling 踏车
myosin 肌球蛋白
kinesin 驱动蛋白
dynein 动力蛋白
三种protein filament
actin filament(microfilament) 肌动蛋白丝(微丝)
determine the shape of the cell’s surface and are necessary for whole cell locomotion and the pinching of one cell into two
确定细胞表面的形状，是整个细胞运动和将一个细胞夹成两个细胞所必需的
microtubules 微管
determine the position of membrane-enclosed organelles, direct intracellular transport, and form mitotic spindle that segregates chromosomes during cell division
确定膜封闭细胞器的位置，指导细胞内运输，形成有丝分裂纺锤体，在细胞分裂过程中分离染色体
intermediate filament 中间纤维
provide mechanical strength
提供机械强度
motor protein 马达蛋白
可以bind to actin or microtubules
水解ATP获得能量
bind to actin
myosin 肌球蛋白
bind to microtubules
kinesins 驱动蛋白
dyneins 动力蛋白
actin filament
subunit
球状的globular(G-actin) → actin filament(F-actin)
G-actin 里面有一个ATP/ADP
单体状态下里面是ATP
F-actin 有一个minus end和一个plus end
actin filament的形成
nucleation
G-actin形成三聚体trimer
限速步骤
elongation
单体快速连接到已有的寡聚体/链上，F-actin快速增长
steady state
形成稳态，G-actin链接到链上与脱离的速度相同
critical concentration
上去的速度是 kon * C
下来的速度是 koff 不取决于浓度
kon * Cc = koff
treadmilling 踏车
指的是plus end不断增长,minus end不断缩短
Cc(T)<Cc(D)
Cc(minus end)<Cc(plus end)
对actin filament的调控
The Functions of Actin Filaments Are Inhibited by Both Polymer-stabilizing and Polymer-destabilizing Chemicals
令微丝稳定/不稳定的化学物质都会导致微丝功能受损
单体可以调节微丝的形成
PROFILIN COMPETES WITH THYMOSIN FOR BINDING TO ACTIN MONOMERS
AND PROMOTES ASSEMBLY
Actin-Nucleating Factors Accelerate Polymerization and Generate Branched or Straight Filaments
arp2/3
可以分叉
formins
形成素
可以稳定plus end同时可以加单体延伸
accessory proteins微丝结合蛋白
myosin and actin
myosin 肌球蛋白
Actin-based motor proteins
通过ATP进行构象变化
肌肉组织
Sliding of Myosin II Along Actin Filaments Causes Muscles to Contract
myofibrl 肌纤维
肌纤维由好多个肌节连成
sarcomere 肌节
thick filament
由myosin肌球蛋白组成
thin filament
由F-actin和troponin complex肌钙蛋白和tropomyosin原肌球蛋白组成
原肌球蛋白会挡住thin filament上与myosin的结合位点,当有Ca2+时,肌钙蛋白会拉着原肌球蛋白移动,露出与myosin的结合位点,肌肉收缩
microtubules
结构
微管的单体是微管蛋白tubulin
tubulin 又分为 α-tubulin and β-tubulin,是一个异二聚体
Microtubules Are Hollow真空 Tubes Made of Protofilaments原丝纤维
Microtubules Undergo Dynamic Instability
微管处于动态不稳定状态
Microtubule dynamics are profoundly influenced by the binding and hydrolysis of nucleotide.
微管动态深受核苷酸结合和水解的影响
Microtubule Functions Are Inhibited by Both Polymer-stabilizing and Polymer-destabilizing Drugs
If the rate of subunit addition is low
→hydrolysis may occur before the next subunit is added
→ the tip of the filament will then be in the D form.
If the rate of subunit addition is high
→ the filament is growing rapidly
→ a new subunit will be added to the polymer before the nucleotide in the previously added subunit has been hydrolyzed
→the tip of the polymer remains in the T form, forming a GTP cap
组装
组装位置是microtubule-organizing center (MTOC)
Nucleation in many cases depends on the γ-tubulin ring complex (γ-TuRC).
centrosome 中心体
typically recruits more than fifty copies of γ-TuRC.
centrioles中心粒是一对圆柱体的结构
Together with a large number of accessory proteins, the centrioles organize
the pericentriolar material 中心粒外围物质, where microtubule nucleation takes place.
组织微管的蛋白
Microtubule-Binding Proteins Modulate Filament Dynamics and
Organization
Microtubule dynamics inside the cell are governed by a variety of microtubule-associated
proteins(MAPs)
A subset of MAPs can mediate the interaction of microtubules with other cell components.
tau和MAP2都是连在微管上的蛋白,可以令微管形成特定的间隔
比如树突里是MAP2,轴突里是tau
微管里的motor protein
kinesins 驱动蛋白
只能往plus end走
有一个N端(走路)一个C端
dyneins 动力蛋白
可以往两边走
分子很大,结构与myosin和kinesin不同
Dynactin动力蛋白激活蛋白 mediates the attachment of dynein to a membrane-enclosed organelle
微管及其动力蛋白功能
the transport and positioning of membrane-enclosed organelles
the anterograde axonal transport顺向轴突输送 (outward transport)and retrograde axonal transport逆向轴突输送 (inward transport)
intermediate filaments
只在多细胞生物,后生动物中存在,比如脊椎动物,线虫,软体动物存在
在机械应力较多的结构中比较多
不同的intermediate filaments被不同的gene编码,因此可以用于鉴别细胞
结构
单体以及二聚体有极性
8个四聚体形成中间丝
Depends on the Lateral Bundling and Twisting of Coiled-Coils
与前面俩的区别
-不包含结合位点
-无极性,没有马达蛋白
-没有踏车
功能
Intermediate Filaments Impart Mechanical Stability to Animal Cells
