The Cytoskeleton 2: Organization and Behavior Flashcards
(116 cards)
1
Q
What is listeria?
A
pathogenic bacteria that invade your intestinal cells
2
Q
Where is listeria found?
A
unwashed lettuce, animal products, dairy + meats
3
Q
What are the symptoms of listeria?
A
headache stiff neck confusion lost of balance convulsions fever and muscle aches
4
Q
What does listeria cause?
A
Food poisoning, especially if you are immunologically deficient or immunocompromised
5
Q
Pregnant women are _____ time likely to get a listeria infection
A
10
6
Q
What could be the results of listeria infection during pregnancy?
A
miscarriage
stillbirth
newborn death
7
Q
What is the treatment of listeria?
A
IV antibiotics
8
Q
Listeria attaches to ________ on enterocytes
A
receptors
9
Q
What is the unusual behavior of listeria based on
A
actin cytoskeleton and accessory proteins
10
Q
What makes up the comet tails of listeria?
A
actin filaments
11
Q
What are the three types of actin filament accessory proteins?
A
affect actin subunits
affects actin filaments
affects filament bundling, cross linking and attachment to membranes
12
Q
What are the accessory proteins that affect actin subunits?
A
ARP complex
Formin
Thymosin
Profilin
13
Q
Describe the ARP complex
A
nucleates assembly to form weblike, highly branch chains and remains associated with minus end
14
Q
Describe formin
A
nucleates assembly of long, unbranched chains and remains associated with growing plus end
15
Q
Describe thymosin
A
binds actin subunits, prevents assembly
16
Q
Describe profilin
A
binds actin subunits, speeds elongation
17
Q
What are the two types of ARP proteins? How identical are they to actin?
A
Arp2 and Arp3
45% identical
18
Q
The ARP complex nucleates actin filament growth from the _______ end, allowing elongation at the ____ end
A
minus; plus
19
Q
ARP complex requires what?
A
activating factor
20
Q
In absence of the activating factor, Arp 2 and Arp3 are masked by other proteins to prevent them from _______
A
nucleating a new actin filament
21
Q
When the ARP complexes bind to the activating factor, it includes a _________. Which mimics the ______ of actin filament.
A
conformational change; plus end
22
Q
Arp complex binding bypasses the _____ step of filament nucleation
A
rate limiting step
23
Q
Bacteria surface causes local ______ of actin filaments
A
nucleation
24
Q
Listeria presents a surface protein called what?
A
ActA
25
What does ActA do?
activates Arp 2/3 complex causes local nucleation of actin filaments which are cross linked
26
What are the driving force to push cell through cytoplasm?
growing filaments
27
When does the ARP complex work the most efficiently?
When bound to the side of the preexisting actin filament filaments cross linked.
28
Filament branches grow at a _______ angle relative to the original filament
70 degree
29
What are force pushes?
addition of actin branched filament pushes the batter along
30
The actin filaments in cell cortex determine the _____ and ______ of the cell surface
shape; movement
31
What are lamellipdia?
flat protrusive veils
32
What are filopodia or microvilli?
spiky bundles
33
What do formins nucleate the growth of?
straight and unbranched actin filaments
34
Where does formin come from?
dimeric proteins
35
Each formin subunit having a _______ for an actin monomer
binding site
36
How do formin dimers nucleate actin filament polymerization?
capturing two monomers at the plus end or growing end of an actin filament
37
What does thymosin do?
regulation of availability of actin monomers for actin polymerization
38
Thymosin keeps actin monomers ______ so they are readily available for generating ______
soluble, filaments
39
Actin monomers bound to thymosin are in a what state?
a locked state
40
What does profilin do?
recruits actin monomers to the actin filament for polymerization
41
When profilin binds to the actin monomer what happens?
it exposes the site of actin that binds to the plus end of the actin filament
42
Addition of an actin monomer to the filament induces conformational change in the actin that ______ its affinity for proflin
reduces
43
When profilin falls off, what is the result?
actin filament is one subunit longer
44
What accessory proteins affect actin filaments and stabilize?
tropomodulin
tropomyosin
capping protein
45
What accessory proteins affect actin filaments and dissemble?
cofilin
| gelsolin
46
Describe tropomodulin
prevents assembly and disassembly at minus end-stabilizes actin filament- for long lived filament stabilization
47
Describe tropomyosin
stabilizes filament- prevents binding with the proteins
48
Describe capping protein
prevents assembly and disassembly at plus end
49
Describe cofilin
binds ADP actin filaments, accelerates disassembly
50
Describe gelsolin
severs actin filaments and binds to plus end
51
Where is tropomodulin present?
muscles
52
Actin filaments are stabilized by the binding of ______
tropomyosin
53
What happens when actin filaments bind with tropomyosin?
prevents the actin filament interaction with other proteins
54
What do capping proteins bind to?
actin filaments
55
What does the capping protein reduce the rate of?
polymerization and depolymerization
56
What is another name for cofilin?
actin depolymerizing factor
57
Cofilin binds to both ______ filament and ____ ______ subunits
actin; free actin
58
When bound to cofilin why does the filament twist more tightly?
weakens the contacts between actin subunits making the filament brittle and more easy to cut
59
The smaller filaments gelsolin makes are available for what?
elongation or disassembly
60
What accessory proteins contribute to filament bundling, cross linking and attachment to membranes
```
a- actinin
fimbrin
filamin
spectrin
ERM family
```
61
a-actinin and fimbrin are what types of proteins?
bundling proteins
62
What is a bundling protein?
cross links actin filaments into a parallel array
63
filamin is what type of protein?
gel-forming
64
What is a gel forming protein?
holds two actin filaments together at a large angle to each other to create a looser meshwork
65
a-actinin cross links acting filaments into _____ bundles, allowing myosin II to enter to make actin filaments______
loose; contractile
66
fimbrin cross links actin filaments into ____ bundles, excluding myosin II
tight
67
Filamin promotes the formation of loose, highly viscous Gell like networks by clamping together 2 ________
actin filaments
68
Why do cells require actin gel?
to extend membrane projections and helps cells to crawl across a solid surface
69
Where does spectrin attach?
to the membrane
70
If spectrin is defective, what is the result?
fragile red blood cells--hemolytic anemia that can lead to hereditary spherocytosis
71
What is included in the ERM family?
Ezrin, radixin, and moesin
72
What does ERM do?
mediate the attachments between actin and plasma membrane
73
How many binding sites does the ERM family have? and what does each one of them do?
two binding sites
one bind to actin filament
one bind on transmembrane protein
74
What are the three major groups of microtubule accessory proteins?
tublin dimers
microtubules
filament cross linking
75
What are the three types of tubulin dimers?
stathmin
TIPS
y-TuRC
76
What does stathmin do?
binds subunits, prevents assembly
77
What does TIPS do?
(the plus end tracking proteins) remains associated with the growing plus ends and can link them to structures such as membranes
78
What does y-TuRC do?
nucleates assembly and remains associated with minus end
79
__________ are the regular subunits for microtubules
alpha and beta tubulin
80
y- tubulin is involved in what?
nucleation of microtubule growth
81
Where are microtubules nucleated from?
microtubule organizing center (MTOC)
82
Microtubules grow ______ from the MTOC from the _____ end
outward; plus
83
What is the y-tubulin ring complex (y-TuRC) responsible for?
nucleation of microtubule growth
84
The major MTOC of animal cells is the ________
centrosome
85
Microtubule are nucleated at the centrosome at their ______ end, with plus ends pointing outward and now toward the cell _______
minus, periphery
86
What are the different kinds of microtubule accessory proteins?
katanin
MAPs
XMAP215
Kinesin 13
87
What does katanin do?
servers microtubules
88
What do MAPs do?
(microtubule associated proteins)
| stabilize tubules by binding along sides
89
What does XMAP215 do?
a microtubule associated protein that stabilizes plus ends and accelerates assembly
90
What does Kinesin 13 do?
enhances catastrophic disassembly at plus end
91
What microtubule accessory protein alters the filaments stability and mechanical properties?
MAPs
92
MAPs stabilize microtubules against _______
disassembly
93
How many domains do MAPs have? What do each do?
two domains
one for binding to microtubule
one projects outward
94
MAPs stabilizes free ends of microtubule and _____ the switch from a growing to a shrinking state
inhibits
95
XMAP215 stabilizes free ends of microtubule and ____ the switch from a growing to a shrinking state
inhibits
96
Kinesin 13 ______ the rate at which microtubule switches from a growing to a shrinking state
increases
97
How does Kinesin 13 bind to microtubule ends and pry protofilaments apart?
by lowering the activation energy barrier that prevents a microtubule from springing apart
98
What are the types of filament cross linking microtubule accessory proteins?
plectin
| tau, MAP2
99
What does pectin do?
cross linking protein, links microtubules to intermediate filaments
100
What does Tau and MAP2 do?
both cause bundling of microtubules
101
MAP2 has a longer _____ than tau
projecting domain
102
Tau binds to the microtubule where?
N and C termini
103
Where do cytoskeletal motor proteins bind?
polarized cytoskeletal filaments
104
Cytoskeletal motor proteins slide against each other generating force that drives ________
muscle contraction or cell division
105
What are the two major groups of cytoskeleton motor proteins?
kinesins and dyneins
106
What is kinesin?
Protein that uses ATP to walk along microtubule track to move vesicles
107
Which way does kinesin walk?
toward plus end of microtubule
108
Where does kinesin carry its binding site and what for?
carried in tail for a membrane enclosed organelle
109
Which direction does dynein move?
toward minus end
110
What is function of cytoplasmic dynein?
vesicle trafficking, localization of the Golgi apparatus
111
What is the function of axonemal dynein?
specialized for rapid and efficient sliding movements of microtubule that drive the beating of cilia and flagella
112
What are two examples of short term cytoskeletal structures?
mitotic spindle
| those assisting with crawling across a solid surface: cell migration
113
Cells must produce ________
polarity
114
What is chemotaxis?
cell movement in a direction controlled by a gradient of a diffusible chemical
115
Where do neutrophils move?
move toward a source of bacterial infection by detecting peptides that are derived form of bacteria proteins
116
```
Which of the following items nucleates actin filament growth from the minus end allowing growth at the plus end with repeated rounds of branching nucleation resulting in a highly branched web of actin filaments (as seen in Listeria infections of enterocytes)?
A. Profilin
B. Gelsolin
C. ARP 2/3 Complex
D. Formin
E. g-TURC
```
C. ARP 2/3 Complex
