北京大学：《分子细胞生物学》课程教学资源（PPT课件讲稿，英文版）Chapter 10 Cytoskeleton System

Chapter 10 Cytoskeleton System 1. Introduction A. Conception of Cytoskeleton_(Narrow sense) A complex network of interconnected microfilaments microtubules and intermediate filaments that extends throughout the cytosol. Microtubules Microfilaments Intermediate filaments

Cytoskeleton System A. Conception of Cytoskeleton (Narrow sense) A complex network of interconnected microfilaments, microtubules and intermediate filaments that extends throughout the cytosol. Chapter 10 Microbubules Microfilamemts Intermediate filaments 1. Introduction

Actin waner false inown a mco mern are two stranded helical polymers of the protein actin. They appear as flexble structures. t ameter of 5-3 nm, that are organised into a van flaments are dispersed throughout the cell, per are.a. Although 二 st highly oncentrated in the corea jus beneath the plasma membrane. 25 mm m Microtubules are long and straight and typically h single mcrotutule-organdring canter (MTOC TLHMIC病 EPILAMENTS afe elaments ate topehke hens with a diameter of around siamen forms a meshwork estee ous family. One type of intermediae bert ore cef-cell 5 Figure 10-2. The three types of protein filaments that form the cytoskeleton

Figure 10-2. The three types of protein filaments that form the cytoskeleton

B Techniques for studying the cytoskeleton o Fluorescent microscopy and Electron microscopy: Immunofluorescence: fluorescently-labeled antibody Fluorescence: microinject into living cells Video microscopy: in vitro motility assay Electron: Triton X-100, Metal replica o Drugs and mutations(about functions) Biochemical analysis (in vitro

B. Techniques for studying the cytoskeleton ❖ Fluorescent microscopy and Electron microscopy : Immunofluorescence: fluorescently-labeled antibody Fluorescence: microinject into living cells Video microscopy: in vitro motility assays Electron: Triton X-100, Metal replica ❖ Drugs and mutations (about functions) ❖ Biochemical analysis(in vitro)

C. The self-assembly and dynamic structure of cytoskeletal filaments Each type of cytoskeletal filament is constructed from smaller protein subunits. The cytoskeleton is a network of three filamentous structures o The cytoskeleton is a dynamic strucrure with many roles

C. The self-assembly and dynamic structure of cytoskeletal filaments ❖Each type of cytoskeletal filament is constructed from smaller protein subunits. ❖The cytoskeleton is a network of three filamentous structures. ❖The cytoskeleton is a dynamic strucrure with many roles

2. Microfilament MF A MFS are made of actin and involved in cell motility. o Using atP, g-actin polymerizes to form MF(F-actin) s on actin molecule NH COOH ATP (ADP when minus end

2. Microfilament, MF A. MFs are made of actin and involved in cell motility. ❖Using ATP, G-actin polymerizes to form MF(F-actin)

ATP ADP DEPOLYMERIZATION POLYMERIZATION ADP ATP) Figure 16-51 The trapping of ADP in an actin filament

Figure 16-51 The trapping of ADP in an actin filament

B MF assembly and disassembly Characteristics: (I)Within a me, all the actin monomers are oriented in the same direction, so MF has a polarity Mru end Aunm (pointed)end (a) Brief treatment with trypan Hinge Myosin is region molecular motor for +o。 Myosin Light meromyosin actins (b)Further treatment with tryosin uttragment 2 Pus end 025m Plum (barbed) end (c) EM and diagram of SI fragments "decorating" actin s1) crofllaments

B. MF assembly and disassembly ❖Characteristics: (1) Within a MF, all the actin monomers are oriented in the same direction, so MF has a polarity Myosin is molecular motor for actins

(2) In vitro, (Polymerization) both ends of the mf grow, but the plus end faster than the minus Because actin monomers tend to add to a filament's plus end and leave from its minus end----Tread-milling 8900

(2) In vitro, (Polymerization) both ends of the MF grow, but the plus end faster than the minus. Because actin monomers tend to add to a filament’s plus end and leave from its minus end---- “Tread-milling

(3)Dynamic equilibrium between the G-actin and polymeric forms, which is regulated by ATP hydrolysis and G-actin concentration ADPATP actin with actin with bound ADP bound ATP

(3) Dynamic equilibrium between the G-actin and polymeric forms, which is regulated by ATP hydrolysis and G-actin concentration

(4) Dynamic equilibrium is required for the cell functions. Some MFs are temporary and others permanent (B)

(4) Dynamic equilibrium is required for the cell functions. Some MFs are temporary and others permanent