Final: Ch 17 Actin Filament Assembly, Cell Structures Flashcards Preview

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Flashcards in Final: Ch 17 Actin Filament Assembly, Cell Structures Deck (31):
1

the rate-limiting step of actin polymerization is what

formation of the actin nucleus that a filament grows from

used as a regulation point

2

2 major classes of actin nucleating proteins are

the formin protein family, and the Arp 2/3 complex

controlled by signal transduction pathways

3

formins lead to the assembly of _____ actin filaments, whereas the Arp2/3 complex leads to _______ networks

long, branched

4

2 important domains of formins

FH1 and FH2 domains

bind actin subunits (FH2) and block CAP protein

increase concentration of profilin-ATP-G-actin complexes (FH1)

5

how is formin regulated

membrane bound Rho-GTPase

when it is switched from Rho-GDP --> Rho-GTP, it binds and activates formin

6

formins assemble long actin filaments like....

stress fibers

filopodia

contractile ring

7

Arp2/3 interacts with what to become a nucleator

nucleation promoting factor (NPF)

allows Arp2 and Arp3 to change into the correct conformation

binds branch at 70 degrees to side of actin filament

8

intracellular movements can be powered by _____ __________

actin polymerization

b/c ATP hydrolysis

9

intracellular bacterial parasite Listeria monocytogenes

food-borne parasite that causes mild GI problems

to move from one host cell to another it polymerizes actin into a comet tail

when it reaches the membrane, it pushes itself inside

10

how does Listeria polymerize actin

has a surface protein called ActA that mimics a NPF to activate Arp2/3

11

actin assembly powers what type of endocytosis

fluid-phase

12

endocytosis assembly factors recruit __s so as the endocytic vesicles invaginate, they are propelled into the cytoplasm

NFPs

causes a short-burst of actin polymerization using the Arp2/3 complex

13

phagocytosis

WBC engulf pathogens

uses microfilaments and myosin motor proteins to draw the pathogen into the cell

14

fungi and sponges have toxins that target the polymerization cycle of actin...one class increases the monomer pool

cytochalasin D - depolymerizes actin by binding + end and blocking addition of monomers

latrunculin - binds G-actin to prevent its addition

15

class of toxins that shifts the monomer-polymer equilibrium in favor of filaments

jasplakinolide - stabilizes actin dimers

phalloidin - prevents F-actin only from depolymerization

16

____-____ proteins organize actin filaments into bundles or networks

cross-linking proteins

17

to be able to organize actin, an actin cross-linking protein must have two...

F-actin binding sites

18

fimbrin

a cross-linking protein w/ 2 actin binding sites found in microvilli that builds bundles of actin filaments with the same polarity

found in microvilli, filopodia, focal adhesions

19

a dimeric cross-linking protein has what

1 actin binding site

2 chains associated into dimers that bring 2 actin binding sites together

20

alpha-actinin

a dimeric cross-linking protein that forms a rigid rod connecting two binding sites

found in stress fibers, filopodia, muscle Z lines

21

spectrin

cross-linking protein found in the cell cortex of RBC

makes networks under the plasma membrane to hold cell together during transport

anemia if mutation (low O2 delivery)

22

filamin

cross-linking protein with a flexible region that makes stabilizing cross-links between filaments in a mesh

found in the leading edge, stress fibers, filopodia

23

the Arp2/3 complex is also an important _____-_____ protein

cross-linking protein

binds the - end of one filament to the side of another filament

24

_____ proteins link actin filaments to membranes

adaptor proteins

ex. in RBC

25

how do RBC survive pumping by the heart, flowing through arteries, and squeezing through capillaries

a microfilament based network with tensile strength and flexibility

based on short actin filaments stabilized on their sides by tropomyosin and the capping protein tropomodulin (-) end

26

mutations in which proteins cause anemia in humans

spectrin

band 4.1

ankyrin

27

what is the orientation of actin filaments in microvilli

+ end at the tip

28

adherens junctions

specialized regions of the plasma membrane where epithelial cells contact each other

29

focal adhesions

specialized regions that mediate attachment of cells to the ECM

30

dystrophin

a protein that links the cortical actin network of muscle cells to the ECM

absence causes muscular dystrophy

31

what is the purpose of cross-linking actin filaments

structural support - holds cell together