Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
36 Cards in this Set
- Front
- Back
|
What are 7 things the Actin Cytoskeleton are responsible for?
|
1. Complex dynamic network
2. interact with MT and IF 3. Control cell shape 4. Critical for membrane integrity 5. Controls organelle movement 6. Controls cell movement 7. Controls cell,tissue, organism contractility |
|
|
What is the most abundant protein in cells?
|
Actin (5-30% total cell protein)
|
|
|
Is actin highly conserved?
|
Yes. mutations/polymorphisms are rare
|
|
|
How many actin genes are there?
|
There are 6 cell specific expressions. 4 muscle and 2 non-muscle
|
|
|
What are the 4 types of actin muscle isozymes?
|
Skeletal
cardiac vascular smooth visceral smooth (GI) |
|
|
What are the 2 types of actin isoforms in non-muscle?
|
β-cytoplasmic in cell cortex
γ-cytoplasmic in stress fibers |
|
|
What is the (-) end of actin called?
|
cleft end
|
|
|
What is the (+ end of actin called?
|
hinge end
|
|
|
What are the properties of monomeric actin?
|
-Globular protein
-Polar (clam shell) -ATPase |
|
|
What are the properties of an actin polymer?
|
Filamentous actin (F-actin)
5 nm wide polar helical twisted chain |
|
|
What is the critical concentration?
|
The concentration of acin at which spontaneous assembly occurs.
|
|
|
What is actin steady state equilibrium?
|
There is an equilibrium between monomer and polymer actin
|
|
|
What does actin need to grow?
|
Assembly competent actin.
ATP = good ADP = Bad |
|
|
What are actin sequestering proteins?
|
They affect assembly competency. Some help exchange ADP for ATP, others block release of ADP...
|
|
|
What is profilin?
|
A sequestering protein that helps exchange ADP for ATP
|
|
|
What is cofilin or thymosin?
|
Sequestering proteins that block the release of ADP by binding to the minus end of the actin monomer. Also prevents addition to F-actin (+) end
|
|
|
What occurs when ATP is hydrolyzes to ADP
|
It changes the shape of actin and destabilizes the polymer. More likely to disassemble and is less assembly competent.
|
|
|
What side of an actin polymer does fast growing occur on?
|
The (+) end. Slow growing takes place on the (--) end
|
|
|
What regulates actin structures, organization, and function?
|
Actin associated proteins. The bind directly to actin and reg by kinase/phosphatase action.
|
|
|
What do actin filament stabilizing molecules do?
|
They laterally associates with F-actin to prevent disassembly. They also block the binding of severing proteins. Ex: Tropomyosin
|
|
|
Which end of actin is barbed?
|
The (+) end is barbed and the (-) end is pointed.
|
|
|
What is gelsolin?
|
It severs F-actin and creates more free (-) ends. Blocks addition to capped (+) end
|
|
|
What is cofilin?
|
It severs F-actin and creates more minus ends. It also traps ADP and blocks addition to the (+) end
|
|
|
What are properties of network/cross-linked actin?
|
flexible, actin at different angles, gel
|
|
|
What are properties of bundled actin?
|
rigid, parallel, spacing controlled, controls motor protein access to actin
|
|
|
What is Myosin?
|
The actin filament motor (very similar to kinesin) 15 known varieties. Move vesicles on actin. Anchor different structures to actin.
|
|
|
How does F-actin help the membrane?
|
It anchors/regulates receptors and other membrane proteins. It also ties membrane to other actin structures and strengthens PM to resist tearing.
|
|
|
What are Rho family GTPases?
|
They universally regulate actin. (Rho, Rac, Cdc42). They control phosphotases and kinases
|
|
|
How does Actin control cell contractility?
|
F-actin is pulled past F-actin via myosins. Occurs in non-muscle and muscle.
|
|
|
What is listeria?
|
It is a bacterial infection that hides from immune system. Infects membrane protrusions using AAPs
|
|
|
What is phalloidin?
|
It is a death cap that hyper-stabilizes F-Actin and blocks disassembly. This a is a fungal toxin
|
|
|
What is Cytochalasins?
|
It is a fungal toxin that sequesters monomers to bind + end F-actin. This blocks polymerization
|
|
|
What happens if actin or AAPs are mutated?
|
Myopathies, hearing loss, cell movement defects, membrane stability defects, dysplasia, carcinogenesis
|
|
|
What are spectrin/fodrin?
|
This is a super family fond in all cells. Is like chainmail under membrane. Maintains cell shape and organization of membrane. Links actin to ECM
|
|
|
What are the properties of spectrin?
|
It forms a tetramer. Flexible rod, two antiparallel dimers (alpha-beta), has ABD1 at ends
|
|
|
Are mutations in binding domains serious?
|
Yes, they are more serious to protein function than spacer domains. can form muscular dystrophy.
|
