Actin Flashcards
How many domains in G actin
4
What does G actin turn into
F actin
What is the step size of actin
36nm
What makes actin polar
ATP-binding cleft
What ways do the arrows point
Always towards the negative end
What does myosin S1 do
Form arrowheads and stabalize the actin
What end does polymerization of actin occur preferentially at
The positive end
What is the critical concentration of the negative end
0.60
What is the crtical concentration of the positive end
0.12
What happens if you are above or below CC
Above you are polymerizing and if you de polymerzing if below
What if you have something in between the two numbers
Treadmilling
What do you need for polymerization
G-actin bound to ATP
What does Thymosin do
Sequesters actin and provides a reservoir
What does profilin do
Promotes actin polymerization by changing G-ADP into G-ATP actin
What is Cofilin
enhances depolymerization
What does Cap z do
Will prevent assembly and disassembly binds to positive end
What does Tropomodulin do
Binds to the negative end and prevents assebly and disassembly
What does Cytochalasin do
Depolymerizes actin fillaments
What does Phallodin do
Stabalizes actin filaments
What are formins
Act as nucleating portiens and regulate assembly of unbranched filaments
What end does formin regulate
Positive
What regulates formin
RHO-GTP
What does Arp 2/3 mediate
Filament branching
What does Arp 2/3 need
Nucleation promoting factor such as wasp or wave that they have to be activated by Cdc24 and Rac
What does WASp go with
Cdc42
What does Wave go with
Rac
What is listeria
It activates ARP 2/3 without Rac and moves arounf very quicky
What can Arp 2/3 also do
Can end in endocytosis which is pulling the plasma membran into the cell and aid is phagocytosis which is pushing the membrane out
What form bundels
Fimbrin and alpha actin (unbranched fillaments)
What are networks
Spectrin and Filamin linked by other protiens
What do Red blood cell depend on
Actin network binding protiens to support the cell membrane (ankyrin)
What does ezrin do
Help the microvilli be stable by attaching to the membrane
What does ankyrin do
Link and anchor the network to the membrane
What does Dystrophin do
Pulls on the PM of the cell if the muscle cell is being pulled
What is myosin
Actins motor protien have heavy and light chains atpase head beck binds light chain tail binds cargo
Whatis class one of myosin
Works alone has one heavy chain support the PM tail attacheed to the membrane head to actin endocytosis
What is class two of myosin
Found in muscle
Organize themselves
Heavy chains are in the middle and contract to the positive end
What is class three of myosin
2 heavy chains
organelle transport
Membrane association/support contraction and transport positive end directed
What effects the sliding speed
The length of the neck makes it go faster
What is a single head step
72nm
What happens when you add ATP
ADP is switched and the head lets go anc causes a recation
Which end does the actin filament bind to
The positive end myosin is bound to
What makes the head bind to the actin filament
When Atp is hydrolized
What is the power stroke
Once it binds a Pi is released and elastic energy straightens myosin moving actin filament left
What is the A band
Myosin 2 filaments they do not change size is is the thick fillament
What comes closer together during contraction
Z disks
What decreases in size
I band
What is the I band
Is where the A band isn’t
Where is the actin found
Between the Z disks
What happens to the A band when it is contracted
It stays the same
What does the Z disks have
CapZ
What extends from Z disk
Titin (like a spring that helps muscles strech and return back)
What centers everything
Nebulin
Where does Ca flood in muscle cells
The Sacroplasmic reticulum
What opens up the Ca channels
An electric signal
Why are there low levels of calcium
With phoshpate it makes a perciptate
What does Ca do when it binds to…..
Troponin and tropomyosin shifts their actin filament exposing myosin binding sites
