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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
cytoskeleton
bundles
networks
myosin
3 cytoskeletal components are: (3) fig 17.2
actin
intermediate
alpha and beta tubulin
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 _-_.
alpha actin
beta actin
gamma actin
Cell signaling regulates cytoskeleton dynamics of cell _, cell _, organelle _, organelle _, etc. fig 17.3
shape
polarity
distribution
movement
Microfilaments can be organized in: (3)
bundles
2D networks
3D networks
_ holds together the two lobes of the actin monomer which has a -/+ end. fig 17.5
aka _-actin
ATP
G-actin
G-actin assembles into long, helical _-actin polymers aka _. ATP is slowly _ to _ in this.
fig 17.5
F-actin
filamentous
hydrolyzed to ADP
F-actin has _ and _ polarity and grows at the +/- end. On + ATP cleft is covered. fig 17.6
structural and functional
+
Actin polymerization in vitro is in 3 steps: fig 17.7
nucleation- slow step
elongation
steady state
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
G-actin
F-actin
below
above
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)
+
-
Cc
treadmill
cytochalais D, latrunculin, phalloidin
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
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
_ nucleate F-actin formation from the + end. fig 17.14. this can be regulated
Formins
the _ complex nucleates branched filament assembly. fig 17.15 goes through a conformational change when _ activation domain is added.
Arp2/3
WASp
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
Actin cross-linking proteins bridge actin filaments to form _ and _. fig 17.18
bundles
networks
Attachment of microfilaments to membranes using _ proteins. fig 17.19 e.g. RBC PM
adaptor
_ 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
myosin
Ca2+ binding
nucleotide-binding
_ _ walk along actin filaments which uses _ as it walks toward _ end and also filaments slide toward _ end. Step size depends on _ _ _.
myosin heads
ATPase
+
-
neck domain length
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
myosin make up a large family of _ motor proteins
mechanochemical
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
muscle is a specialized contractile machine that consists of _ > _ > _.
myofiber, myofibril, sarcomere
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
myosin, actin
myosin II
+
CapZ
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
myosin make up a large family of _ motor proteins
mechanochemical
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
muscle is a specialized contractile machine that consists of _ > _ > _.
myofiber, myofibril, sarcomere
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
myosin, actin
myosin II
+
CapZ
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
_ for stretch and _ for measure are accesory protein filaments that organize the _. fig 17.31
titin
nebulin
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
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
actin
myosin II
light chain phosphorylation (MLC)
calmodulin
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
non-muscle
sheets or belts
belt
stress fibers
_ _ carries membrane-defined cargoes like vesicles and organelles toward + end. fig 17.36
Myosin V
Controlled polymerization and rearrangements of actin filaments occur during cell movement or _. Steps are: (4) fig 17.38
locomotion
extension, adhesion, translocation, de-adhesion
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.
PM
G-actin-ATP
thermal
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
Arp2/3
cofilin, gelsolin
+