Cytoskeleton 2 Flashcards
Intermediate Filament Function
Cell structure, localization of cellular processes.
Anchors cells
Intermediate filament structure
Central rod domain (a helix), amino head,carboxy tail.
Strongest and most stable cytoskeleton protein
Forms network
Keratin expressed in
Epithelial cells
Intermediate filament assembly
Dimers —> tetramer (anti parallel and staggered) -> protofilament —> 8 protofilaments form filament from both ends
Epidermolysis bullosa simplex (EBS)
Most common and mildest EB.
Keratin defective, skin splits at epidermis causing blisters
Microtubules assembly
- Dimers of hollow a and B tubulin polymerizing using GTP to give microtubules.
- 13 protofilaments arranged around hollow core.
- (+) and (-) end
Dynamic instability of Microtubules
- individual microtubules alternate between growth and shrinkage.
- GTP-tubulin added faster than GTP cleaved then growth and vice versa.
- rapidly = “catastrophe”
Microtubule Centrosome
Organizing center, initiates growth.
-binds (-) end and allow growth toward plasma membrane
y-tubulin
Key protein for microtubule growth from centrosome.
Microtubule stability
Unstable but stabilized by post translation modifications and microtubule associated proteins (MAPs)
MAPs (polymerases/depolymerases) 5 things
- Specific.
- regulate microtubules by capping ends
- speeds up assembly/dissembly by increasing/dissociating GTP tubulin at (+) end
- connect microtubules to IFs or plasma membrane
- binds to GTP and moves growing microtubules
CLASP
An MAP that rescues microtubules from catastrophe by stopping disassembly and restarting growth at (+) end.
- clamps around microtubule
Microtubule that sends signals in nerve cells
Axons. Project from cell body
Microtubule that receives signals in nerve cells
Dendrites. Project from cell body.
Axons
(+) end away from main part (cell body)
- (-) end not anchored in centrosome
- capped at both ends
- Contain tau protein that stabilizes
