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39 Cards in this Set
- Front
- Back
actin filaments are one of the 3 protein filament systems that comprise the _. They're in eukaryotic cells in _: mainly structural, In _: dynamic, movement, with a motor of _.fig 17.1
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cytoskeleton
bundles networks myosin |
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3 cytoskeletal components are: (3) fig 17.2
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actin
intermediate alpha and beta tubulin |
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Actin facts: up to 10% of muscle cell protein, 1-5% in other cell types, Humans have a 6 member gene family with 4 _-_, 1 _-_, and 1 _-_.
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alpha actin
beta actin gamma actin |
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Cell signaling regulates cytoskeleton dynamics of cell _, cell _, organelle _, organelle _, etc. fig 17.3
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shape
polarity distribution movement |
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Microfilaments can be organized in: (3)
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bundles
2D networks 3D networks |
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_ holds together the two lobes of the actin monomer which has a -/+ end. fig 17.5
aka _-actin |
ATP
G-actin |
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G-actin assembles into long, helical _-actin polymers aka _. ATP is slowly _ to _ in this.
fig 17.5 |
F-actin
filamentous hydrolyzed to ADP |
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F-actin has _ and _ polarity and grows at the +/- end. On + ATP cleft is covered. fig 17.6
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structural and functional
+ |
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Actin polymerization in vitro is in 3 steps: fig 17.7
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nucleation- slow step
elongation steady state |
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The critical conc (Cc) is the conc of _-actin in equilibrium with _-actin. _ Cc F-actin doesn't form and _ Cc F-actin forms until =Cc. fig 17.8
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G-actin
F-actin below above |
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Actin filaments grow faster at the _ end than the _ end bc _ is lower on the + end so G-actin subunits _ down toward - end. fig 17.10 Actin can be interupted by (3)
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+
- Cc treadmill cytochalais D, latrunculin, phalloidin |
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Binding proteins influence polymerization: fig 17.11 and has 3 important proteins used:
_- binds G-actin, promoting exchange of ADP for ATP and promoting assembly into _-_. _- binds and breaks F-actin, creating more _ ends for disassembly _-_ binds ATP-G-actin, preventing its incorporation into F-actin and formain a reservoir of G-actin |
profilin
F-actin cofilin - thymosin-beta4 |
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Capping of proteins affects dynamics: if you: fig 17.12
cap - end then you have _. cap + end then you have _. cap both the you have a _ _. |
growth
depolymerization stable filament |
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_ nucleate F-actin formation from the + end. fig 17.14. this can be regulated
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Formins
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the _ complex nucleates branched filament assembly. fig 17.15 goes through a conformational change when _ activation domain is added.
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Arp2/3
WASp |
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Actin polymerization can power _ movement: e.g. Listeria is pushed forward by polymerization. fig 17.17 where it uses:
_ _- to get + end to grow |
intracellular
Act A |
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Actin cross-linking proteins bridge actin filaments to form _ and _. fig 17.18
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bundles
networks |
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Attachment of microfilaments to membranes using _ proteins. fig 17.19 e.g. RBC PM
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adaptor
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_ is the actin motor proteins.It has heavy chains (HMM-heavy meromyosin) and light chains are used as regulatory subunits usually _-_. fig 17.20 _-_ site uses ATP to walk down filament
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myosin
Ca2+ binding nucleotide-binding |
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_ _ walk along actin filaments which uses _ as it walks toward _ end and also filaments slide toward _ end. Step size depends on _ _ _.
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myosin heads
ATPase + - neck domain length |
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Dif in myosin tail domains determines dif in function. 3 classes:
_ - normal, short, single neck; used for membrane association and endocytosis _ - organelle transport, membrane associated on organelles, vesicles and the PM for vesicle transport _ - tails pack together, form thick filament; in skeletal muscles, very thick and bipolar. fig 17.23 |
Class I
Class V Class II |
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myosin make up a large family of _ motor proteins
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mechanochemical
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model of myosin movement along F-actin: fig 17.24
1 ATP binds to _ _ to release from actin 2 _ of _ to ADP causes head to rotate and become cocked. 3 head binds to _. 4 "_ _" involves the release of P elastic energy to straighten myosin and move actin filament to left. 5 _ is released and _ is bound to release head again. fig 17.24 |
1myosin head
2hydrolysis, ATP 3actin 4power stroke 5ADP, ATP |
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muscle is a specialized contractile machine that consists of _ > _ > _.
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myofiber, myofibril, sarcomere
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Thick (_) and thin (_) filaments slide past one another during contraction.The bipolar thick fibers walk toward _ end of thin fibers. There is a _ at the + ending. 17.30
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myosin, actin
myosin II + CapZ |
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Dif in myosin tail domains determines dif in function. 3 classes:
_ - normal, short, single neck; used for membrane association and endocytosis _ - organelle transport, membrane associated on organelles, vesicles and the PM for vesicle transport _ - tails pack together, form thick filament; in skeletal muscles, very thick and bipolar. fig 17.23 |
Class I
Class V Class II |
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myosin make up a large family of _ motor proteins
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mechanochemical
|
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model of myosin movement along F-actin: fig 17.24
1 ATP binds to _ _ to release from actin 2 _ of _ to ADP causes head to rotate and become cocked. 3 head binds to _. 4 "_ _" involves the release of P elastic energy to straighten myosin and move actin filament to left. 5 _ is released and _ is bound to release head again. fig 17.24 |
1myosin head
2hydrolysis, ATP 3actin 4power stroke 5ADP, ATP |
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muscle is a specialized contractile machine that consists of _ > _ > _.
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myofiber, myofibril, sarcomere
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Thick (_) and thin (_) filaments slide past one another during contraction.The bipolar thick fibers walk toward _ end of thin fibers. There is a _ at the + ending. 17.30
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myosin, actin
myosin II + CapZ |
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Capping both f-actin ends stabilizes filaments and is important where cytoskeleton organization is _ as in muscle sarcomere and erthrocyte membranes.
+ end cap- _ - end cap- _ |
unchanging
CapZ Tropomodulin |
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_ for stretch and _ for measure are accesory protein filaments that organize the _. fig 17.31
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titin
nebulin |
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A rise in cytosolic Ca2+ triggers muscle contraction using various pumps and channels. fig 17.32
A skeletal muscle is kept in a _ Ca2+ states by SR _-Class pump. fig 11.10 nerve impulse at junction opens a SR _ channel increasing the cytosolic level Ca2+-dependent conformational change in _-_ exposes myosin binding sites on actin, allowing contraction. fig 17.33 |
low
P-class Ca2+ tropomyosin-troponin |
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Ca2+ also regulates smooth muscle contraction: In skeletal muscle, regulation by turning _ on and off. In smooth muscle, regulation by turning _ _ on and off via _ _ _ (_). Ca2+ activates MLC kinase through _ which phosphorylates MLC to activate myosin II. fig 17.35
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actin
myosin II light chain phosphorylation (MLC) calmodulin |
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Actin and Myosin II form contractile bundles in _-_ cells. This is present in PM as _ or _. During cytokinesis the belt contracts that wraps around junction of cells. _ fibers are involved in cell anchoring and movement. fig 17.34
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non-muscle
sheets or belts belt stress fibers |
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_ _ carries membrane-defined cargoes like vesicles and organelles toward + end. fig 17.36
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Myosin V
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Controlled polymerization and rearrangements of actin filaments occur during cell movement or _. Steps are: (4) fig 17.38
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locomotion
extension, adhesion, translocation, de-adhesion |
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Controlled polymerization and rearrangements of actin filaments occur during cell movement:leading edge: rapid dynamic push the _ where Profilin delivers _-_-_ to the + end of F-actin. _ motion facilitates ability to add to + end at the membrane.
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PM
G-actin-ATP thermal |
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Controlled polymerization and rearrangements of actin filaments occur during cell movement: leading edge: _ causes branching and growth with - end cap. _ and _ sever f-actin and promote disassembly from the - ends. capping _ end stops growth and disassembly cycle to begin again. fig 17.39
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Arp2/3
cofilin, gelsolin + |