Actin & Cell Motility and Muscle Contraction

Cytoskeleton
1. Microtubules
2. Microfilaments
3. Intermediate filaments
Actin
1. Globular actin
2. Filament actin
The structure of actin and actin filaments
1. form bundles & network
  1. Bundles
  2. Networks
2. both B&N maintained by proteins that link them together
3. other proteins bind them to membranes
4. play in movement within cell
  1. assembly/disassembly of filaments
  2. trades for movement of motor protein
Branching of actin filaments and cell movement
1. Polymerisation of G-actin
  1. Nucleation
  2. Elongation
  3. Steady state
    1. preferential polymerisation at the (+) end
      1. depolymerisation at the (-) end
2. Role of accessory protein in actin assembly
  1. Profilin
    1. recharge ADP-G-actin to ATP-G-actin to ATP-F-actin
  2. Actin-related protein
    1. Branching of actin daughter filaments
  3. Gelsolin/cofilin
    1. actin-severing proteins 'breaking' the actin filaments & capping the (+) end
3. Cell movement
  1. Chemotaxis
    1. Extension of lamellipodia
    2. Adhesion of lamellipodia
    3. Flow of cytosol
    4. Retraction of the rear of the cell
    5. happens because of actin polymerisation & depolymerisation
Motility of myosin motor proteins on actin filaments
1. Myosin head properties
2. ATP hydrolysis --> movement of myosin along an actin filament
  1. hydrolysis of ATP generates 'power stroke' --> moves myosin
The contractile apparatus of muscle
1. Interaction of myosin and actin --> contraction of muscle
  1. muscle cells has repeating arrays of filament bundles (sarcomere)
    1. Actin filaments (thin)
    2. Myosin filaments (thick)
    3. The sliding filament model shows myosin pulls actin filaments towards the centre of sarcomere
Regulation of striated and smooth muscle contraction

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Actin & Cell Motility and Muscle Contraction

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Medienanhänge

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