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Mbb231 > Cytoskeleton-MF > Flashcards

Cytoskeleton-MF Flashcards

1
Q

Smallest cytoskeletal filament

A

Microfilament
Actin filament
F-actin

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2
Q

MF are known for

A

Their role in muscle contraction

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3
Q

Building blocks of MF is

A

Actin

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4
Q

Actin is

A

Highly conserved globular protein

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5
Q

Actin types

A

Alpha-actin: muscle specific actin
Betta-actin: apical
Gamma-actin: basal

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6
Q

Most abundant in all eukaryotic cells

A

Actin

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7
Q

Actin after synthesis

A

Folds into globular U-shaped molecule that can bind ATP or ADP

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8
Q

G-actin (globular actin) will

A

Polymerize to form microfilaments (F-actin) filamentous actin

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9
Q

MF hydrolyze —— but MT hydrolyze ——

A

ATP
GTP

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10
Q

G actin can polymerize reversibly to

A

Filaments with lag phase, elongation phase

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11
Q

F-actin

A

Composed of two linear strand of polymerized G-actin wound into helix

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12
Q

All actin filament have——

A

Same orientation

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13
Q

Actin filament

A

-two stranded helical polymer
-concentrated beneath the plasma membrane
-easily change cell morphology by assembling/disassembling (Dynamic)
-MF have polarity
-Requires ATP (actin is ATPase)

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14
Q

Polarity of MF reflect on

A

More rapid addition of G-actin at + end than - end

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15
Q

After G actin assembles onto MF,

A

ATP bound to them slowly hydrolyzed
hydrolysis is not required for polymerization

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16
Q

Growing end has

A

ATP actin

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17
Q

Most of Mf has

A

ADP actin

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18
Q

Treadmilling can occur in

A

MT and MF

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19
Q

Cells can regulate how MF are assembled such as

A

1- Cell that crawl: Lamellipodia and Filopodia at leading edge
2- cell that adhere tightly: stress fibers

20
Q

—— organize and behave the MFs

A

Actin binding proteins

21
Q

Actin binding proteins

A

1- ARP complex
2- Thymosin Betta 4
3- CapZ/ Tropomoduli
4- Formin
5- Cofilin
6- Filamin/ alpha-actinin
7- Gelsolin
8- Spectrin/Ankyrin

22
Q

Thymosin Betta-4

A

Bind to (+ end) ATP-actin monomer and prevent them from polymerization

23
Q

Profilin

A

Binds to ADP-G-actin catalyze the exchange ADP to ATP, promoting polymerization

24
Q

Cofilin

A

Bind (- end) ADP-actin in MF, severe it promote depolarization

25
Q

Capping proteins

A

CapZ: bind to + end, prevent addition/loss of subunit

Tropomodulin: bind to - end, prevent addition/loss of subunit

physically binding

26
Q

Sever actin filaments

A

Gelsolin: break actin MF and caps the newly exposed + end

Cofilin: filament-severing proteins, facilitating depolarization

27
Q

Formins

A

Control the assembly of actin filament
Nucleate polymerization of unbranched actin filament
Associated with + end, enabling rapid insertion of actin filament and protect the end from capping proteins

28
Q

Some Formins have extensions that can bind

A

Profilin

29
Q

Cross link filaments

A

Filamin: join two MF together

30
Q

Bundle actin filament

A

Fimbrin: bundle Mf in microvilli

31
Q

Link MF to membrane

A

One or more peripheral membrane proteins: spectrin and Ankyrin

32
Q

Nucleate new filaments

A

Arp2/3 complex: nucleate new branches, tree-like network

33
Q

Intermediate filament

A

Are not polarized
Support the cytoskeleton by acting as scaffold(bridging molecules) between Mt and MF

34
Q

Intermediate filament assemble from

A

Fibrous Subunits rather than globular

35
Q

Intermediate filament

A

-Central rod-shaped alpha-helix domain that is conserved
-Has N-terminus and C-terminus that differ greatly
-unlike MT and MF can be made of many different proteins
-have only been found in animals
- expression vary from tissue-to-tissue

36
Q

Intermediate filament classified based on

A

Degree of AA

37
Q

N terminus and c terminus sequence and structure can vary the most as they can binding site for

A

-intermediate filament
-MF
-MT

38
Q

—— can help in diagnosis of certain tumors

A

Intermediate filament

39
Q

Tumor cells

A

Lose morphological appearance but retain cytoskeletal proteins

By using of antibodies against IF can determine if origin is epithelial, mesenchymal, neural

40
Q

IF proteins synthesize

A

-Primarily fibrous molecules, globular domain on each end
-two polypeptide spontaneously interact, wrapping around each other, create dimer
Two dimer assemble creating anti-parallel tetramer(no polarity)
Eight tetramers pack laterally to form one unit
Unit associate with each other to form elongated IF

41
Q

Unlike MF and MT, in IF,

A

Units are not removed from ends, rather the interior

42
Q

IF assembly does not

A

Require energy (ATP or GTP)

43
Q

IF mechanical strength

A

MT resist bending
MF generate tension
IF elastic and withstand tensile forces
IF are most stable cytoskeleton component
IF are not static, dynamically remodeled

44
Q

IF examples

A

Nuclear Matrix
Nuclear Lamina
Both supporting structures

45
Q

Nuclear matrix (nucleoskeleton)

A

Insoluble fibrous network
Maintains the shape of nucleus
Attachment site for chromatin

46
Q

Nuclear Lamina

A

Thin dense fibers lining the inner surface of inner nuclear membrane
-made of IF composed of Lamina
-disassemble prior to mitosis by phosphorylation of Lamins

Mbb231 (19 decks)

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