Cytoskeleton and Motor Proteins Flashcards
- Draw/describe intermediate filaments, including subunit types, arrangement,
construction/destruction, structure and function
Solid, unbranched. Strong polypeptide fibers that are subject to stress. Connected to other filaments by cross bridges, made of plectin a lot. contain a central, rod-shaped, α-helical domain of similar length and homologous amino acid sequence with globular domains on each side of variable sequences. The basic building block of IF assembly is thought to be a rodlike tetramer formed by two dimers that become aligned side by side in a staggered fashion with their N- and C-termini pointing in opposite (antiparallel) directions, as shown in Figure 9.36a, step 3, and in Figure 9.36b. Because the dimers point in opposite directions, the tetramer itself lacks polarity. Eight tetramers associate with one another in a side-by-side (lateral) arrangement to form a filament that is one unit in length (about 60 nm) (step 4).
Subsequent growth of the polymer is accomplished as these unit lengths of filaments associate with one another in an end-to-end fashion to form the highly elongated intermediate filament (step 5). None of these assembly steps is thought to require the direct involvement of either ATP or GTP. Because the tetrameric building blocks lack polarity, so too does the assembled filament, which is another important feature that distinguishes IFs from other cytoskeletal elements.
Draw/describe microtubules, including subunit types, arrangement, construction/destruction,
structure and function
o Explain/draw the foundational structures of microtubule formations, such as basal
bodies, MTOCs, axonemes, etc.
- Draw/describe microfilaments, including subunit types, arrangement, construction/destruction,
structure and function
- Explain the structure of motor proteins associated with each of the cytoskeletal protein
structures, as well as their method of movement along their respective cytoskeletal proteins,
including any specific subtypes of these motor proteins, directions the motor proteins
specifically move, and what is accomplished by this movement
o Dynein
o Kinesin
o Myosin - NOTE: The Table 9.1 is very helpful in putting together many elements for each of the
cytoskeletal protein types - NOTE: The videos uploaded to Canvas’ Media Gallery, as well as others can be helpful to visualize
the processes of movement
Actin (ATPase) monomer binds to ATP, but is hydrolyzed to ADP after it’s incorporated into polymer
Steps for actin being added-
- Actin filaments present with actin surrounding it
- Subunits added to both ends as long as concentration is high
- Concentration drops as subunits are added until net monomers added at barbed end, which has a lower critical concentration of ATP actin but stops at the pointed end
- Concentration falls until 2 reactions are balanced (addition at both ends, concentration of free units is constant), atp actin concentration is ~.3 MicroM
Can the rate of actin addition be altered?
Yes, via accessory proteins, which can reorganize a cells cytoskeleton
What do actin filaments do?
Motile processes
ACtin structure
filaments made of actin subunits, most abundant protein. Polymerize in presence of ATP. 2 stranded structure with 2 helical grooves along length. Can be in ordered arrays, highly branched networks, or tightly anchored bundled depending on location and function. Monomers all pointed in the same direction. Barbed is +, pointed is -.
Actin filament AKA
f-actin, microfilaments
What does Actin do?
Contractile protein in muscle cells, but major component of all eukaryotic cells. Can hybridize with other actin molecules to make hybrids. Usually requires motor proteins to work, specifically myosin ones. Critical for cell motility, muscle contraction, cell division, cytokinesis.
