Intermediate Filaments Flashcards

1
Q

What is the size generally of Intermediate Filaments?

A

10 nm

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2
Q

TRUE OR FALSE:
Inermediate Filaments have HIGH tensile strength?

A

True

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3
Q

What are the SIX differences in Intermediate Filaments from microfilaments and microtubules?

A
  1. No bound nucleotides
  2. Not polar
  3. No motor proteins
  4. Less dynamic
  5. Subunits are more diverse
  6. Not found in plants / fungi
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4
Q

How many classes / families of Intermediate Filaments are there?

A

5
* all share 310 AA α-helical rod domain
* Non-helical head and tail domains differe between classes

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5
Q

How is the structure of an Intermediate Filament formed?

A

Rod domains dimerise through formation of a coiled-coil

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6
Q

What is the basic building block of Intermediate Filaments?

A

Dimers

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7
Q

How do two dimers combine in Intermediate Filaments?

A

Staggered anti-parallel fashion

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8
Q

TRUE OR FALSE:
Intermediate Filaments have polarity?

A

False

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9
Q

How are Intermediate Protofilaments formed?

A

Tetramers assemble end-to-end

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10
Q

What is formed when 4x Protofilaments are combined?

A

Protofibril

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11
Q

What is formed when 4x Protofibrils are combined?

A

Mature Intermediate Filament

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12
Q

What proteins are found in CLASSES I & II of Intermediate Filaments, where are they found and what is their function?

A
  • Acidic Keratins - Class I
  • Basic Keratins - Class II
  • Function: Tissue strength and integrity
  • Location: Epithelial cells
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13
Q

What proteins are found in CLASS III of Intermediate Filaments, where are they found and what is their function?

A
  • Desmin, GFAP, Vimentin
  • Location: Muscle, Glial, and Mesenchymal cells
  • Function: Sarcomere organisation & integrity
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14
Q

What proteins are found in CLASS IV of Intermediate Filaments, where are they found and what is their function?

A
  • Neurofilaments
  • Location: Neurons
  • Function: Axon organisation
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15
Q

What proteins are found in CLASS V of Intermediate Filaments, where are they found and what is their function?

A
  • Lamins
  • Location: Nucleus
  • Function: Nuclear structure and organisation
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16
Q

How many different Acidic and Basic Keratin subunits form dimers?

A

50

17
Q

Where are Hard Keratins found?

A

Hair and nails

18
Q

What gives Hard Keratins their strength?

A

Disulphide bonds between abundant cysteines

19
Q

Where are Soft Keratins found?

A

Epithelial cells

20
Q

What is the function of Soft Keratins?

A

Strengthen and support cells

21
Q

What TWO junctions do Soft Keratins associate with?

A
  1. Desmosomes
  2. Hemidesmosomes
22
Q

What are Desmosomes?

A

Junctions between adjacent cells

23
Q

What are Hemidesmosomes?

A

Junctions between cells and extracellular matrix

24
Q

What disease is caused by mutations in Keratins?

A

Epidermolysis Bullosa Simplex
* skin disease characterised by blistering

25
Q

What is the function of Lamins?

A

Strengthen and support the nuclear membrane

26
Q

How many types of Lamins are there?

A

2
* Type A and Type B

27
Q

What causes Lamin association with inner surface of the nuclear membrane?

A

Isoprenylation of Type B Lamins

28
Q

What happens to Lamins during Mitosis?

A

Lamins are phosphorylated by a cyclin-dependent kinase
* key step in disassembly of the nuclear membrane

29
Q

What diseases are caused by mutations in Type A Lamins?

A
  • Emery-Dreifuss muscular dystrophy
  • Hutchinson-Gilford progeria (premature ageing)
30
Q

What gene is mutated in Hutchinson-Gilford progeria?

A

LMNA gene

31
Q

How does the mutation of the gene in Hutchinson-Gilford progeria affect Type A Lamin?

A

Production of a truncated form that disrupts the nuclear lamina network