BGM1002/L04 Non-Globular Proteins

Question 1

Name 3 structural proteins.

Answer 1

Keratin
Silk
Collagen

Question 2

Name a fibrous/filamentous protein.

Answer 2

Cytoskeletal proteins

Question 3

Name 3 globular proteins that assemble into fibrous quaternary arrangements. (3)

Answer 3

Cytoskeletal proteins
Flagellae
Pilli
Filamentous viruses

Question 4

Give 3 features of protein fibres.

Answer 4

Strong
Dynamic
Can interact with other proteins in DNA

Question 5

Why don’t bacteria need a cytoskeleton for shape?

Answer 5

Their cell wall provides their shape.

Question 6

Give 3 functions of the cytoskeleton.

Answer 6

Links membrane to nucleus in eukaryotes
Provides mechanical stability
Provides template for cell wall construction in some organisms

Question 7

Give the 3 components of the cytoskeleton.

Answer 7

Microfilaments
Intermediate filaments
Microtubules

Question 8

What are microfilaments primarily made from?

Answer 8

Actin

Question 9

How does actin contribute to the function of microfibrils?

Answer 9

Actin binds and hydrolyses ATP

Question 10

Which end does actin 1) bind at and 2) dissociate at?

Answer 10

1) Positive end
2) Negative end

Question 11

Which proteins (2) sequester free actin?

Answer 11

Profilin & gelsolin

Question 12

Name 4 features of intermediate filaments.

Answer 12

Long
Strong
Elastic
Flexible

Question 13

What are intermediate filaments formed from?

Answer 13

Long coiled-coil proteins that may have globular ends at termini

Question 14

Give 3 functions of intermediate filaments.

Answer 14

Cell adhesion
Cellular organisation
Muscle fibres

Question 15

What type of intermediate filaments are keratins?

Answer 15

I & II

Question 16

Name the 2 Type III intermediate filaments.

Answer 16

Vimentin & Desmin

Question 17

Name the 2 Type IV intermediate filaments.

Answer 17

Alpha-internexin & synemin

Question 18

Name the Type V intermediate filament.

Answer 18

Lamins

Question 19

Name the 2 Type VI intermediate filaments.

Answer 19

Nestin & Filensin

Question 20

Describe the structure of Keratin.

Answer 20

Superhelices formed by coiled coils

Question 21

Name 5 structures made from alpha-keratin.

Answer 21

Hair
Skin
Claws
Nails
Feathers

Question 22

Name 3 structures made of beta-keratin.

Answer 22

Scales
Nails of reptiles
Tortoise shells

Question 23

How is keratin’s coiled-coil structure stabilised?

Answer 23

Hydrophobic interactions

Question 24

How is keratin formed?

Answer 24

Dimers multimerise to form tetramers and so on, to produce filaments.

Question 25

Describe the structure of Vimentin.

Answer 25

Coiled coil of eight tetramers, stuck together to form fibrous filaments

Question 26

How is Vimentin formed?

Answer 26

Dimerisation and formation of antiparallel tetramer

Question 27

What is the function of Vimentin?

Answer 27

Anchors organelles in cytoskeleton

Question 28

Name the 2 key proteins of neurofilaments.

Answer 28

Alpha-interexin & nestin

Question 29

Describe the structure of Lamin (3).

Answer 29

Long alpha-helix with one globular domain present Polymers organised into protofilaments Coiled-coil domain and terminal head

Question 30

What is the function of Lamin? (2)

Answer 30

Structure and regulation of nucleus Feedback to cell on mechanical stress

Question 31

What are microtubules composed of?

Answer 31

Alpha and beta tubulin.

Question 32

What charge does 1) the beta end and 2) the alpha end of microtubules have?

Answer 32

1) Beta +ve 2) Alpha -ve

Question 33

What end does elongation occur more rapidly in microtubules?

Answer 33

Beta/ positive end

Question 34

How many protofilaments form a helical filament in microtubules?

Answer 34

13

Question 35

What does MTOC stand for?

Answer 35

Microtubules Organising Centre

Question 36

What is the key MTOC in the cell?

Answer 36

Centrosomes

Question 37

What does the drug Taxol do?

Answer 37

Inhibits cell cycle & stabilises GDP-bound tubulin Cancer drug

Question 38

What is the function of microtubule-related proteins?

Answer 38

Regulate microtubule stability

Question 39

What do molecular motors do (2)?

Answer 39

Traffic vesicles in cells Endo-exocytosis

Question 40

What proteins are present in muscle fibres? (5)

Answer 40

Actin Myosin Troponin Tropomyosin Titin

Question 41

What is special about the protein Titin?

Answer 41

Biggest known protein Prevents over-extension

Question 42

What is the singular protein subunit in flagellae?

Answer 42

Flagellin

Question 43

Name an example of a filamentous virus.

Answer 43

Filamentous bacteriophage Tobacco Mosaic Virus Some influenza viruses

Question 44

What kind of structure protects genetic material in filamentous viruses?

Answer 44

Helix

Question 45

What is the function of pilli?

Answer 45

Cell-cell recognition for transfer of genetic information

Question 46

What protein do pilli consist of?

Answer 46

Pillin

Question 47

Describe the structure of pillin.

Answer 47

Globular domain with long alpha-helix filaments

Question 48

What is the diameter of pillin's helical arrangement?

Answer 48

6-7 nm

Question 49

What are fimbriae?

Answer 49

A surface attachment/ hair-like extension on some archaea and bacteria

Question 50

What are curli fibres?

Answer 50

Amyloid fibres produced by enterobacteria

Question 51

What structure does collagen consist of?

Answer 51

Triple helix of 2 a1 chains and 1 a2 chain

Question 52

What 3 amino acids is collagen rich in?

Answer 52

Glycine, proline and hydroxyproline

Question 53

Give two examples of diseases related to collagen-deficiency.

Answer 53

Scurvy Ehlers-Danlos Epidermolysis bullosa

Question 54

Give 2 examples of animals that produce silk.

Answer 54

Silkworm Hymenoptera (bees, wasps, ants) Spiders Lacewings

Question 55

What percentage of fibroin and sericin does silkworm silk contain?

Answer 55

70-80% fibroin 20-30% sericin

Question 56

Give 2 general properties of spider silk.

Answer 56

Highly ductile High tensile strength

Question 57

Describe the structure of spidroin.

Answer 57

Repetitive glycine and alanine rich blocks Beta-strand regions with disordered regions

Question 58

Give 3 types of spidroins.

Answer 58

MaSp1 MaSp2 Flagelliform

Question 59

What type of proteins don't have regular tertiary structures?

Answer 59

Intrinsically disordered proteins

Question 60

Give 3 examples of diseases caused by misfolded proteins/accumulation/aggregation.

Answer 60

Alzheimer's Parkinson's ALS CJD Type II diabetes

Question 61

What 3 proteins are most susceptible to misfolding?

Answer 61

Alpha-synuclein Beta-amyloid Prion

Question 62

What kind of dye is used for amyloids?

Answer 62

Congo red dye