Intermediate Filaments Flashcards

1
Q

The Intermediate Filament Multigene Family:

A

Type I: Keratins 9-20 (Acidic), Epithelials cells e.g. desmosomes
Type II: Keratins 1-8 (Basic), Epithelials cells e.g. desmosomes
Type III: Desmin, Vimentin, GFAP, skeletal muscles e.g. Desmin surrounds the sarcomere
Type IV: Neurofilaments, Axon organisation
Type V: Lamins, Nuclear structure and organisation
Type VI: Filensin

All have similar secondary structure (alpha helical coiled coils)

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2
Q

Intermediate Filaments are Polar.

TRUE OR FALSE

A

FALSE

Intermediate filaments are apolar. They exchange subunits along the whole filament.

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3
Q

Structure of Intermediate Filaments

A

Head domain: essential for filament assembly

Alpha-helical rod domain: assembles in parallel dimers then antiparallel tetramers (Between head and tail domains). Then 8 tetramers are twisted into a rope-like filament.

Tail domain: contributes to filament assembly

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4
Q

Heptad repeats

A

A type of tandem repeat sequence in which a group of seven amino acids occurs many times in a protein sequence.
They form the basis of coiled-coil formation in intermediate filament protein dimers.

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5
Q

Intermediate filaments are difficult to bend, but are susceptible to stretching.
TRUE OR FALSE

A

FALSE
Intermediate filaments resist stretching but are easily bent.
Due to having staggered long subunits (Like long bricks). They have 8 tetramers twisted into a rope-like filament.

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6
Q

Keratin intermediate filament proteins:

A

Type I Proteins: Acidic isoelectric points (pH at which the molecule has no net charge)
Type II Proteins: Neutral or basic isolelectric points
Equimolar association of Type I and II required for assembly
Specific paired expression in tissues.

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7
Q

Intermediate filament attachment sites:

A

Keratins: Desmosomes and Hemidesmosomes

Type III: Desmosomes (Desmin/GFAP)

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8
Q

What happens when intermediate filaments fail? (In terms of disorders)

A

Skin blistering disorders arise (such as Epidermolysis bullosa simplex)

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9
Q

Intermediate filaments in the nucleus:

A

Lamin (Type V) intermediate filaments are all intranuclear.
A-lamins in differentiated cells.
B-lamins in all nuclei.
Disassembly/reassembly of the nuclear lamina by phosphorylation at mitosis.

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