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Biology Exam 2 > Cytoskeleton: Proteins > Flashcards

Cytoskeleton: Proteins Flashcards

1
Q

pathogenic bacteria that invades intestinal cells

A

listeria

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2
Q

how does the pathogenic bacteria discussed in this lecture move?

A

actin based motility
speed boats around the cell leaving a actin comet tail

based upon ARP 2/3 complex

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3
Q

accessory proteins act up _____ filaments, and either (3)?

A

actin or microtubules

subunits, filaments, bundling/cross-linking

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4
Q

3 categories of actin proteins

A
  1. affect subunits
  2. affect filaments
  3. affect bundling, cross-linking, attachment of actin to membrane
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5
Q

ARP 2/3 complex

A
  • nucleates assembly to form web-like/highly branched chains
  • remains on the minus end
  • allows rapid growth at plus end
  • works best w/ existing filaments at a 70 degree angle
  • responsible for listeria mvts
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6
Q

made up of 2 proteins, 45% identical to actin

A

ARP

ARP 2 + ARP 3 = ARP 2/3 complex

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7
Q

ActA

A

activation factor of the ARP 2/3 complex

  • required for ARP to bind to the minus end
  • binding causes conformational change
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8
Q

what does ActA do?

A

allows ARP 2/3 complex to skip the rate limiting step of polymerization

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9
Q

nucleates assembly to form highly branched chains at 70 degree angles w/ pre-existing filaments

A

ARP 2/3 complex

affects actin subunits

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10
Q

formin

A

nucleates assembly of long straight chains

  • remains w/ plus end
  • a large dimeric protein
  • each subunit has binding site for actin monomer
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11
Q

nucleates assembly of long straight chains

A

formin

affects actin subunits

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12
Q

thymosin

A

binds actin monomers to prevent assembly

-keeps monomers soluble so they are ready for polymerization

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13
Q

_____ bound to thymosin are ……?

A

actin monomers
in a locked state
-cannot associate w/ actin filaments

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14
Q

binds actin monomers to prevent assembly

A

thymosin

affects actin subunits

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15
Q

profilin

A

binds actin monomers to speed up elongation

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16
Q

profilin mechanism steps

A
  1. binds to a monomer
  2. exposes binding site for plus end on the monomer
  3. monomer binds to plus end
  4. profilin falls off
  5. ready to begin again
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17
Q

why does profilin not stay associated?

A
  • monomer binds to plus end
  • induces conformational change in actin
  • affinity for profilin is reduced
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18
Q

binds to actin monomers to speed up elongation

A

profilin

affects actin subunits

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19
Q

proteins that affect actin subunits

A
  1. ARP 2/3
  2. thymosin
  3. profilin
  4. formin
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20
Q

proteins affecting actin filaments will either _____ or _____ .

A

stabilize or promote disassembly

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21
Q

proteins stabilizing actin filaments

A
  1. tropomodulin
  2. tropomyosin
  3. capping protein
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22
Q

tropomodulin

A
  • stabilizes actin by preventing assembly and disassembly

- keep long lived filaments

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23
Q

for long lived actin filaments

A

tropomodulin

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24
Q

tropomyosin

A
  • stabilizes actin by preventing the binding of other proteins
  • key protein in RBC cytoskeletons
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25
Q

stabilizes actin by preventing the binding of other proteins

A

tropomyosin

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26
Q

stabilizes actin by preventing addition and loss

A

tropomodulin

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27
Q

capping protein

A

stabilizes actin by protecting the plus end from addition and loss
-binds to plus end

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28
Q

protects the plus end from addition and loss, to stabilize actin filaments

A

capping protein

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29
Q

proteins promoting disassembly of actin filaments

A
  1. cofilin

2. gelsolin

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30
Q

cofilin

A

increases loss rate by binding to ADP-actin filaments and causing monomers to be freed

disassembles whilst tropomyosin stabilizes

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31
Q

results of cofilin binding

A
  • binds to ADP-actin filament
  • causes it to twist more tightly
  • thus weakening the subunits contact
  • filament is then brittle and easily cut
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32
Q

relate cofilin to listeria

A

responsible for removing the comet tail in its wake

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33
Q

increases rate of disassembly by binding to ADP-actin filaments and freeing monomers

A

cofilin

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34
Q

gelsolin

A

severs actin filaments and binds to plus end

  • results in smaller filaments available for add/loss
  • helps with rapid shrinkage or growth
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35
Q

binding of gelsolin can result in 2 outcomes, what determines which one?

A

can cause rapid shrinkage or growth

-depends upon the conditions of the cell

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36
Q

severs actin filaments and binds to the plus end

A

gelsolin

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37
Q

proteins affecting bundling, cross-linking, and membrane attachment of actin filaments

A
  1. alpha-actinin
  2. fimbrin
  3. filamin
  4. spectrin
  5. ERM family
38
Q

actin filament bundling proteins

A
  1. alpha-actinin
  2. fimbrin
  3. filamin
39
Q

alpha-actinin

A
  • actin filament bundling protein

- cross link actin filaments in parallel loose bundles

40
Q

what is the significance of actin bundles being loose?

A

allows myosin II to enter

-thus making actin filaments contractile (skeletal muscle)

41
Q

cross-link actin filaments in parallel loose bundles

A

alpha-actinin

42
Q

fimbrin

A
  • actin bundling protein

- cross link actin filaments in parallel tight bundles

43
Q

what is the significance of actin bundles being tight?

A

can exclude myosin II

-actin filaments will not be made contractile

44
Q

alpha-____ & _____ are capable of excluding each other for ______ .

A

alpha-actinin and fimbrin can exclude each other for different functions

45
Q

cross-link actin filaments in parallel tight bundles

46
Q

filamin

A
  • forms gel like structures
  • holds 2 actin filaments together at a large angle (90)
  • to create a mesh-work structure
47
Q

what is ‘actin get’ required for?

A

in order to extend membrane projections such as needed when crawling

-cells w/o or mutated filamin cannot crawl

48
Q

what cells discussed in lecture is crawling important?

A

macrophages and fibroblasts

49
Q

forms gel like structures

A

filamin

bundling of actin filaments

50
Q

spectrin

A

attaches cytoskeleton to membrane

  • important in RBCs
  • gives cell durability and stability
51
Q

defective spectrin result in ?

A

disease

anemia

52
Q

attaches actin filaments to plasma membrane, especially important in RBCs

A

spectrin

gives RBCs their biconcave shape

53
Q

ERM family members

A
  1. ezrin
  2. radixin
  3. moesin
54
Q

ERM family

A
  • attaches actin filaments to membrane
  • has two binding sites
    1. actin filament
    2. transmembrane protein
55
Q

attaches actin filaments to a transmembrane protein

A

ERM family

56
Q

3 types of microtubule proteins

A
  1. affect tubulin dimers
  2. affect microtubules
  3. affect filament cross-linkages
57
Q

proteins affecting tubulin dimers

A
  1. Stathmin
  2. TIPS
  3. gamma-TuRC
58
Q

stathmin

A

binds to tubulin dimers

-prevents assembly

59
Q

prevents microtubule assembly by binding to tubulin dimers

60
Q

TIPS

A
  • the plus-end tracking proteins
  • remains associated with the growing plus end
  • can link them to structures
61
Q

associated with the growing plus end of microtubules and capable of linking them to structures

62
Q

gamma - TuRC

A
  • gamma tubulin ring complex
  • nucleates assembly/responsible for microtubule assembly
  • remains associated with minus end
63
Q

what serves as a template for microtubule structure

A

gamma-TuRC

for the 13 protofilament - hollow cylinder structure

64
Q

describe the origins of microtubules

A
  • microtubule organizing center = centrosome
  • located near nucleus in cytoplasm
  • > 50 TuRCs associated
  • plus ends grow outward in a star
65
Q

proteins affecting microtubules

A
  1. katanin
  2. MAPs
  3. XMAP215
  4. kinesin 13
66
Q

katanin

A

katana

cuts microtubules

67
Q

MAPs

A
  • microtubule associated protein
  • stabilizes microtubule by binding along the sides to prevent disassembly
  • inhibits switch from growth to loss
  • catastrophe suppressed
68
Q

binding domains of MAPs

A
  1. binding site to microtubule

2. other projects outward

69
Q

cuts microtubules

70
Q

stabilizes microtubules by binding along sides and prevents loss

71
Q

XMAP215 — how it gets it’s name?

A
  • a map protein
  • xenopus map
  • molecular weight = 215 kDa
72
Q

XMAP215

A

stabilizes the plus end of microtubules by binding to plus end and inhibits switch from growth to loss

  • catastrophe suppressed
  • accelerates growth
73
Q

a microtubule stabilizing protein that binds to the plus end and suppresses catastrophe

74
Q

kinesin 13

A
  • promotes catastrophe
  • increases rate at which microtubules switch from growth to loss
  • binds to plus end and pries protofilaments apart
75
Q

how does kinesin 13 achieve it’s goal?

A
  • binds to plus end of microtubule

- pries protofilaments apart by lowering the activation energy barrier (which prevents them from springing apart)

76
Q

protein that promotes catastrophe of microtubules

A

kinesin 13

77
Q

proteins that affect microtubule cross-linking

A
  1. plectin
  2. Tau
  3. MAP2
78
Q

plectin

A
  • microtubule cross-linking protein

- links microtubules to intermediate filaments

79
Q

Tau

A
  • a MAP protein

- causes tight bundling of microtubules

80
Q

Tau factors

A
  • binds to both N and C terminus of microtubule
  • has a short projecting loop
  • forms bundles of more closely packed microtubules
81
Q

MAP2

A
  • causes bundling of widely spaced microtubules

- has a long projecting domain with a second microtubule bound at the other end

82
Q

cross-links microtubules to intermediate filaments

83
Q

tight bundling of microtubules

84
Q

widely spaced bundling of microtubules

85
Q

cytoskeleton motor proteins bind to ?

A

polarized filaments

actin and microtubules

86
Q

motor proteins require ____ to move

87
Q

motor proteins are responsible for causing filament _____ .

A

tension

-can generate force that drives muscle contraction or cell division

88
Q

structure of motor proteins

A
  1. head domain = motor domain

2. tail domain = binds to cargo

89
Q

kinesins

A

-use ATP to walk towards + end

90
Q

dyneins

A
  • composed of 2-3 heavy chains
  • largest and fastest
  • always moves towards minus end
91
Q

cytoplasmic dynein

A
  • vesicle mvt

- localization of golgi

92
Q

axonemal dynein

A
  • specialized

- rapid and efficient sliding mvts that drive the beating cilia and flagella

Biology Exam 2 (9 decks)

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