Cytoskeleton: Proteins Flashcards
(92 cards)
1
Q
pathogenic bacteria that invades intestinal cells
A
listeria
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
3
Q
accessory proteins act up _____ filaments, and either (3)?
A
actin or microtubules
subunits, filaments, bundling/cross-linking
4
Q
3 categories of actin proteins
A
- affect subunits
- affect filaments
- affect bundling, cross-linking, attachment of actin to membrane
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
6
Q
made up of 2 proteins, 45% identical to actin
A
ARP
ARP 2 + ARP 3 = ARP 2/3 complex
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
8
Q
what does ActA do?
A
allows ARP 2/3 complex to skip the rate limiting step of polymerization
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
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
11
Q
nucleates assembly of long straight chains
A
formin
affects actin subunits
12
Q
thymosin
A
binds actin monomers to prevent assembly
-keeps monomers soluble so they are ready for polymerization
13
Q
_____ bound to thymosin are ……?
A
actin monomers
in a locked state
-cannot associate w/ actin filaments
14
Q
binds actin monomers to prevent assembly
A
thymosin
affects actin subunits
15
Q
profilin
A
binds actin monomers to speed up elongation
16
Q
profilin mechanism steps
A
- binds to a monomer
- exposes binding site for plus end on the monomer
- monomer binds to plus end
- profilin falls off
- ready to begin again
17
Q
why does profilin not stay associated?
A
- monomer binds to plus end
- induces conformational change in actin
- affinity for profilin is reduced
18
Q
binds to actin monomers to speed up elongation
A
profilin
affects actin subunits
19
Q
proteins that affect actin subunits
A
- ARP 2/3
- thymosin
- profilin
- formin
20
Q
proteins affecting actin filaments will either _____ or _____ .
A
stabilize or promote disassembly
21
Q
proteins stabilizing actin filaments
A
- tropomodulin
- tropomyosin
- capping protein
22
Q
tropomodulin
A
- stabilizes actin by preventing assembly and disassembly
- keep long lived filaments
23
Q
for long lived actin filaments
A
tropomodulin
24
Q
tropomyosin
A
- stabilizes actin by preventing the binding of other proteins
- key protein in RBC cytoskeletons
25
stabilizes actin by preventing the binding of other proteins
tropomyosin
26
stabilizes actin by preventing addition and loss
tropomodulin
27
capping protein
stabilizes actin by protecting the plus end from addition and loss
-binds to plus end
28
protects the plus end from addition and loss, to stabilize actin filaments
capping protein
29
proteins promoting disassembly of actin filaments
1. cofilin
| 2. gelsolin
30
cofilin
increases loss rate by binding to ADP-actin filaments and causing monomers to be freed
disassembles whilst tropomyosin stabilizes
31
results of cofilin binding
- binds to ADP-actin filament
- causes it to twist more tightly
- thus weakening the subunits contact
- filament is then brittle and easily cut
32
relate cofilin to listeria
responsible for removing the comet tail in its wake
33
increases rate of disassembly by binding to ADP-actin filaments and freeing monomers
cofilin
34
gelsolin
severs actin filaments and binds to plus end
- results in smaller filaments available for add/loss
- helps with rapid shrinkage or growth
35
binding of gelsolin can result in 2 outcomes, what determines which one?
can cause rapid shrinkage or growth
| -depends upon the conditions of the cell
36
severs actin filaments and binds to the plus end
gelsolin
37
proteins affecting bundling, cross-linking, and membrane attachment of actin filaments
1. alpha-actinin
2. fimbrin
3. filamin
4. spectrin
5. ERM family
38
actin filament bundling proteins
1. alpha-actinin
2. fimbrin
3. filamin
39
alpha-actinin
- actin filament bundling protein
| - cross link actin filaments in parallel loose bundles
40
what is the significance of actin bundles being loose?
allows myosin II to enter
| -thus making actin filaments contractile (skeletal muscle)
41
cross-link actin filaments in parallel loose bundles
alpha-actinin
42
fimbrin
- actin bundling protein
| - cross link actin filaments in parallel tight bundles
43
what is the significance of actin bundles being tight?
can exclude myosin II
| -actin filaments will not be made contractile
44
alpha-____ & _____ are capable of excluding each other for ______ .
alpha-actinin and fimbrin can exclude each other for different functions
45
cross-link actin filaments in parallel tight bundles
fimbrin
46
filamin
- forms gel like structures
- holds 2 actin filaments together at a large angle (90)
- to create a mesh-work structure
47
what is 'actin get' required for?
in order to extend membrane projections such as needed when crawling
-cells w/o or mutated filamin cannot crawl
48
what cells discussed in lecture is crawling important?
macrophages and fibroblasts
49
forms gel like structures
filamin
| bundling of actin filaments
50
spectrin
attaches cytoskeleton to membrane
- important in RBCs
- gives cell durability and stability
51
defective spectrin result in ?
disease
| anemia
52
attaches actin filaments to plasma membrane, especially important in RBCs
spectrin
| gives RBCs their biconcave shape
53
ERM family members
1. ezrin
2. radixin
3. moesin
54
ERM family
- attaches actin filaments to membrane
- has two binding sites
1. actin filament
2. transmembrane protein
55
attaches actin filaments to a transmembrane protein
ERM family
56
3 types of microtubule proteins
1. affect tubulin dimers
2. affect microtubules
3. affect filament cross-linkages
57
proteins affecting tubulin dimers
1. Stathmin
2. TIPS
3. gamma-TuRC
58
stathmin
binds to tubulin dimers
| -prevents assembly
59
prevents microtubule assembly by binding to tubulin dimers
Stathmin
60
TIPS
- the plus-end tracking proteins
- remains associated with the growing plus end
- can link them to structures
61
associated with the growing plus end of microtubules and capable of linking them to structures
TIPS
62
gamma - TuRC
- gamma tubulin ring complex
- nucleates assembly/responsible for microtubule assembly
- remains associated with minus end
63
what serves as a template for microtubule structure
gamma-TuRC
| for the 13 protofilament - hollow cylinder structure
64
describe the origins of microtubules
- microtubule organizing center = centrosome
- located near nucleus in cytoplasm
- >50 TuRCs associated
- plus ends grow outward in a star
65
proteins affecting microtubules
1. katanin
2. MAPs
3. XMAP215
4. kinesin 13
66
katanin
katana
| cuts microtubules
67
MAPs
- microtubule associated protein
- stabilizes microtubule by binding along the sides to prevent disassembly
- inhibits switch from growth to loss
- catastrophe suppressed
68
binding domains of MAPs
1. binding site to microtubule
| 2. other projects outward
69
cuts microtubules
katanins
70
stabilizes microtubules by binding along sides and prevents loss
MAPs
71
XMAP215 --- how it gets it's name?
- a map protein
- xenopus map
- molecular weight = 215 kDa
72
XMAP215
stabilizes the plus end of microtubules by binding to plus end and inhibits switch from growth to loss
- catastrophe suppressed
- accelerates growth
73
a microtubule stabilizing protein that binds to the plus end and suppresses catastrophe
XMAP215
74
kinesin 13
- promotes catastrophe
- increases rate at which microtubules switch from growth to loss
- binds to plus end and pries protofilaments apart
75
how does kinesin 13 achieve it's goal?
- binds to plus end of microtubule
| - pries protofilaments apart by lowering the activation energy barrier (which prevents them from springing apart)
76
protein that promotes catastrophe of microtubules
kinesin 13
77
proteins that affect microtubule cross-linking
1. plectin
2. Tau
3. MAP2
78
plectin
- microtubule cross-linking protein
| - links microtubules to intermediate filaments
79
Tau
- a MAP protein
| - causes tight bundling of microtubules
80
Tau factors
- binds to both N and C terminus of microtubule
- has a short projecting loop
- forms bundles of more closely packed microtubules
81
MAP2
- causes bundling of widely spaced microtubules
| - has a long projecting domain with a second microtubule bound at the other end
82
cross-links microtubules to intermediate filaments
plectin
83
tight bundling of microtubules
Tau
84
widely spaced bundling of microtubules
MAP2
85
cytoskeleton motor proteins bind to ?
polarized filaments
| actin and microtubules
86
motor proteins require ____ to move
ATP
87
motor proteins are responsible for causing filament _____ .
tension
| -can generate force that drives muscle contraction or cell division
88
structure of motor proteins
1. head domain = motor domain
| 2. tail domain = binds to cargo
89
kinesins
-use ATP to walk towards + end
90
dyneins
- composed of 2-3 heavy chains
- largest and fastest
- always moves towards minus end
91
cytoplasmic dynein
- vesicle mvt
| - localization of golgi
92
axonemal dynein
- specialized
| - rapid and efficient sliding mvts that drive the beating cilia and flagella
