Cytoskeleton I Flashcards
Roles of cytoskeleton
Cell polarity
Directional migration
Formation of mitotic/meiotic spindle
Chromasome seg
cytokinesis
Intracellular transport, exo/endo cytosis
Why do cytoskeletal components have dif distributions
Important for cell shape, polarity, and tissue formation
What are cytoskeletal structure made of
Small protein subunits Noncovalent polymers Dynamic Accessory proteins regulate sites and state of assembly Adaptable
Intermediate filaments key facts
Intermeidate in size, more stable
Major components of cytoskel and nuclear boundary
Protection from mechanical stress-within cells (surround nun and extend to periphery) and at junction of cell and ECM
Role insignalling and gene reg networks
No motor
Intermediate filaments strucutre
Include keratins, near filaments, nuclear lamins
Two chained coiled coil that assembles to form tetramere-tetramer forms higher order assemblies-held together by hydrophobic interactions
N anC terminal ends are globular-coiled coil region interrupted by linker domains
Intermediate protein assembly
Antiparallel tetrameters
not polar
Actin key facts
Polyermeric and globular (g-actin)
Polar-ends are distinctly different
Bound nucleotide (ATP/ADP)
Plus end (barbed) is fast growing Minus end (pointed) is slower growing)
Helical filament
Binding proteins modify filament dynamics and higher order assemblies
Actin elongation
Faster at plus (barbed) end
Rate limiting step is formation of nucleus (3 subunits)
ATP actin is preferentially added to barbed end
-hydrolysis not required for polyermaization-bound nun influences stability
Each actin filament has ADP-actin, except for extreme barbed end
What do proteins that bind to actin do
Bind to one end (cap)
Sever filaments
Cross link
Anneal etc
MT and actin filament parallels (6)
Both form globular protein by condensation/polymerization mech to form polar structure
Both have pref end of monomer addition
Nuc hydroylsis lags behind polyermization elaving ATP/GTP cap at plus end
Nucleotide at plus end determines stability
Dynamics and state of assembly reg by MT binding proteins
Structures are NOT RELATED
Tubulin and MT structure
Two subunits
- b binds to GTP
- GTP hydrolyzed during polymerization which is at plus end of molecule
- polyermerizes to long protofilaments in MT
Polar
Nothing on the inside
Tubulin and MT function
Vesicular and organelle transport, from mitotic spindle, cilia, and flagella, entriole and basal bodies
What structures are made of MT’s
cilia, flagella, centrioles, and basal bodies
Have knobs coming out of outer doublet (dyenine)
Primary cilium
Apparent on most cells
Non-motile
Usually 1 per cell
Sensory organellles
Central player in dev signaling pathways
No central pair, no knobs oming out of outer doublet (no dyeing)
Centrosome Facts
MT organizing center-all MT eminate from here
- Minus end is located here
- gamma tubulin ring complex that nucleates the 13 protofilaments of MT’s and caps the - ends
- +ends oriented towards cell periphery
- centrioles duplicate at beginning of S phase of mitosis
