Cytoskeleton Flashcards
(43 cards)
what 3 kinds of protein structures is the cytoskeleton made up of
microfilaments (actin)
intermediate filaments
microtubules
what does highly conserved mean
the chemical/molecular structure is very similar among a wide range of different organisms
what are the filaments of actin microfilaments organized into
bundles and 3D networks
what doe actin microfilaments bind to and how
bind to specific transmembrane proteins either directly or indirectly
how do actin microfilaments exists as
monomers (G-actin) and long chains (F-actin)
what are the 3 major varieties of actin filaments
alpha-actin (found in muscle tissue)
beta-actin (non muscle actin)
gamma-actin (non muscle actin)
what is the first step of actin polymerization
nucleation
what occurs during nucleation during actin polymerization
a trimer is formed
addition actin monomers can then be added to either end
what happens following polymerization of microfilaments
ATP-actin associates with the growing (plus or barbed) ends, and the ATP is hydrolyzed to ADP following polymerization
which end of microfilaments is the slower growing end
minus end (pointed or depolymerization end)
what doe very low concentrations of F actin favor
disassembly of actin filaments
what do intermediate concentrations of G actin favor
dynamic equilibrium between the minus end and the plus end (tread milling)
what do high concentrations of G actin favor
net addition at both ends and therefore growth of the actin filament
what does cytochalasins do
drug that affects actin polymerization:
binds to barbed ends, blocks elongation, can inhibit movement
what does phalloidin do
drug that affects actin polymerization
binds to actin filaments and prevents dissociation
can be labeled with fluorescent dyes to allow visualization of actin filaments
what are the actin binding proteins & what do they do
- spectrin: (found in RBC) binds cortical cytoskeleton to the plasma membrane
- dystrophin: binds cortical cytoskeleton to the plasma membrane
- villin and fimbrin: cross-links in microvilli
- calmodulin and myosin I: cross-links actin to plasma membrane in microvilli
- alpha-actinin: cross-links stress fibers and connects actin to protein-plasma membrane complex complexes
- filamin: cross-links actin at wide angles to form screen-like gels
what are the actin-binding molecules that control treadmilling
- thymosin: captures actin monomers and prevents actin monomers from being polymerized
- profilin: binds to actin monomers and prevents monomers form being polymerized, facilities exchange of bound ADP for ATP-favors polymerization
- gelsolin: destabilizes F-actin and caps actin filaments (preventing loss and addition of G-actin)
- cofilin: triggers depolymerization of ADP-bound actin at the minus end
- Arp2/3: initiates growth of F actin from sides of existing filaments-causes branching
- phalloidin: prevents depolymerization by binding to actin filaments
- latrunculins: binds to G-actin and induces F-actin depolymerization
what does spectrin do?
(found in RBC) binds cortical cytoskeleton to the plasma membrane
what does dystrophin do
binds cortical cytoskeleton to the plasma membrane
what does villain and fimbrin do
cross-links in microvilli
what does calmodulin and myosin I do
cross-links actin to plasma membrane in microvilli
what does alpha-actinin do
cross-links stress fibers and connects actin to protein-plasma membrane complex complexes
what does filamin do
cross-links actin at wide angles to form screen-like gels
what does thymosin do?
(tread milling)captures actin monomers and prevents actin monomers from being polymerized
