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cytoskeleton features Flashcards

1
Q

the cytoskeleton is made up of 3 structures, which are…

A

Microfilaments (7nm), intermediate filaments (8-10 nm), and microtubules (25 nm)

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2
Q

Actin: how many genes do I have? What are my varieties?

A

6.
4 are expressed in muscle cells and 2 in non-muscle cells.

alpha-actin (found in muscle)
beta-actin (non-muscle actin)
gamma (non-muscle actin)

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3
Q

T/F: Actin does not bind directly to transmembrane proteins?

A

False: it binds directly or indirectly

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4
Q

Actin monomers = ___? Actin filaments = ____ ?

A

G-actin and F-actin

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5
Q

“Treadmilling” refers to-

A

equilibrium between polymerization and depolymerization of G-actin to F-actin

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6
Q

Low concentrations of G-actin favor what process?

A

depolymerization

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7
Q

High concentrations of G-actin favor what process?

A

polymerization

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8
Q

What end of F-actin does G-actin polymerize most quickly?

A

the plus (+) end, barbed

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9
Q

the “slow” moving end of F-actin is called the

A

minus ( - ) end, the pointed end

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10
Q

Cytochalasins

A

Prevents elongation, interrupts mitotic spindle: does job by binding to + end of f-actin

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11
Q

Phalloidin

A

Binds to actin filaments and prevents their depolymerization

Fluorescent-labeled phalloidin is used to stain actin filaments in cells

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12
Q

Latrunculins

A

Disrupts actin polymerization by binding to g actin and inducing f-actin depolymerization

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13
Q

Profilins

A

Has two functions: can exchange ADP for ATP on G-actin, favoring polymerization at barbed end OR it can prevent G-actin from polymerization by holding on to molecule monomer

“Suppresses nucleation”

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14
Q

Cofilin

A

An actin depolymerization factor: stimulates dissociation of ADP bound g-actin

Triggers depolymerization at the minus end

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15
Q

Thymosin

A

Sequesters pools of g-actin monomers within a cell.

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16
Q

Gelsolin

A

Dual role: capping protein to prevent loss and addition of actin monomers; a severing protein

Destabilizes f actin and caps actin filaments, preventing loss and addition of g actin

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17
Q

Spectrin

A

RBC relation actin binding protein, connects cytoskeleton to plasma membrane

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18
Q

Dystrophin

A

Connects cytoskeleton to plasma membrane

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19
Q

Villin and fimbrin

A

Cross connecting proteins in microvilli

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20
Q

Calmodulin

A

Cross links actin filaments to microvilli cytoplasm

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21
Q

Myosin 1

A

Cross links actin filaments to microvilli cytoplasm

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22
Q

Alpha actinin

A

Cross links stress fibers and connects actin to cytoplasm complexes

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23
Q

Filamin

A

Cross links actin at wide angles to form screen like gels

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24
Q

Parallel bundles

A

Closely spaced f-actin fibers with the same polarity

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25
Contractile bundles
Utilizes alpha actinin: actin fibers spaced widely apart, cross connected by alpha actinin
26
What causes nucleation?
Random collisions, which explains the high rate of polymerization when concentrations of actin are high
27
What stabilizes actin as formins nucleate along unbranched stretches of f-actin?
tropomyosin
28
Intermediate filaments are ___ thick, and are ___ in all cells subject to ___________
8-10 nm, abundant, mechanical stress
29
What do intermediate filaments do per say?
Provide tensile strength in cells such as neurons and muscle
30
IF: All have a common monomer consisting of-
a central alpha helical rod flanked by a head and tail domain
31
I consist of repeating amino acid segments: what am I, what's my name?
intermediate filament, "heptads"
32
Coiled-coil alpha helix dimers OR parallel _________. What am I?
intermediate filaments
33
Structure of the intermediate filaments (5 levels)
a. polar filament monomer (N end/C end) align like polar groups, forming a DIMER b. dimers align in antiparallel fashion, forming a TETRAMER c. tetramers coil around one another to form PROTOFILAMENTS d. protofilaments align to form PROTOFIBRILS e. 4 protofibrils coil together to form a 10 nm thick intermediate filament
34
What aspect of intermediate filaments allow them to bind to other elements in the cytoskeleton?
the N terminal and C terminals
35
T/F The formation of a nonpolar helical structure consisting of two nonpolar antiparallel tetramer requires ATP to occur.
F, no ATP involved. Spontaneous.
36
IFAPS: What am I, what is my role, and how might I operate?
Intermediate filament associated proteins (IFAPS) Stabilize filaments by cross linking adjacent filaments or by linking to other cytoskeletal elements May cap filaments to prevent further elongation
37
IFAPS: list 'em
``` Filaggrin (associated with keratin) Epinemin Paranemin Plectin Synemin ```
38
Synemin
IFAP
39
Epinemin
IFAP
40
Filaggrin
IFAP, associated with keratin
41
Plectin
IFAP
42
Paranemin
IFAP
43
Type I IF Type
Acidic Keratins along with basic to neutral keratins, these form the intermediate filaments of the epithelial cell cytoskeleton
44
Acidic Keratins
form the intermediate filaments of the epithelial cell cytoskeleton associated with plaques of desmosomes and hemidesmosomes
45
Type II
Basic Keratins, along with acidic keratins they form the intermediate filaments of the epithelial cell cytoskeleton
46
Vimentin
Type III IF, found in mesenchymal cells
47
Desmin
Type III IF, associated with sarcomeric Z-discs
48
Glial fibrillary acidic protein
Type III IF associated with astrocytes and Schwann cells (glial cells)
49
Peripherin
Type III IF associated with neurofilaments
50
Neurofilaments
Type IV IF, found in axons and dendrites
51
Nuclear Lamins
Type V nuclear lamins: provide mechanical support for inner membrane of nuclear envelope and bind chromatin
52
Nestin
Type VI IF associated with CNS stem cells
53
Microtubules are ____ in width, and composed of ____ and _____
25 micrometers alpha (negatively charged end) and beta (positively charged)
54
A "protofilament" in the microtubulin category consists of
a longitudinal row of tubulin
55
Microtubules are composed of
alpha and beta tubulin dimers strung together to form long rows of them
56
A microtubule is composed of
13 protofilaments arranged parallel to form a cylinder with a hollow core
57
13 is the magic number for what molecule?
microtubules: the number of protofilaments in a "microtubule"
58
Dynamic instability refers to
"alternating phases of slow growth and rapid depolymerization"
59
What causes dynamic instability?
the hydrolysis of GTP tubulin dimers, which release GDP dimers subunits
60
MAPs ---->
microtubule associated proteins: increase stability of microtubules
61
Factors that inhibit microtubule polymerization--->
colchicines, colcemid, vincristine, and vinblastin: bind to tubulin monomers and inhibits polymerization
62
Factors that inhibit depolymerization and stabilize microtubules
taxol: binds to microtubule and inhibits depolymerization
63
Cilium: structure
9 peripheral doubles + central pair of microtubules
64
Each doublet consists of
alpha tubule: this consists of 13 protofilaments, radial spokes extending to sheath around central pair, and pairs of dynein arms projecting to beta unit of next doublet
65
alpha tubule
consists of 13 protofilaments, radial spokes extending to sheath around central pair, and pairs of dynein arms projecting to beta unit of next doublet
66
beta tubule
10-11 protofilaments
67
13 protofilaments = the
alpha tubule
68
10-11 protofilaments = the
beta tubule
69
which protofilament has the dynein arm stretching to its neighbor?
the alpha
70
which protofilament contains spokes which radiate toward the sheath around the central pair?
the alpha
71
rod like portion refers to what cytoskeletal component and what is it called
IF, formed by polymerization of long, rod like elements coiled-coil alpha helix dimers or parallel intermediate filament proteins referred to as "heptad"

cell bio cytoskeleton composition (2 decks)

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