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Structure, Function And Analysis Of Proteins > SFP13: Structural Proteins > Flashcards

SFP13: Structural Proteins Flashcards

1
Q

What are general characteristics of structural proteins?

A
  • Long, filamentous
  • Generally, insoluble
  • Contain unusual amino acids
  • Often contain cross-linked polypeptide chains
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2
Q

Name some extracellular structural proteins

A
  • Keratin
  • Collagen
  • Elastin
  • Resilin
  • Fibrillin
  • Fibrin
  • Spidroin
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3
Q

Name cellular structural proteins

A

Filamentous muscle proteins

Cytoskeleton proteins

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4
Q

What three components make up alpha-keratin?

A

Glutamic acid/ glutamine
Cystine
Serine

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5
Q

What are characteristics of alpha-keratins?

A

Coiled-coil; each stand is a distorted right handed alpha-helix

Double alpha-helical coiled-coil; left handed supercoiling

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6
Q

What are characteristics of beta-keratins?

A

Extended chains

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7
Q

What organisation structure does chain packing in alpha keratin take?

A

Heptane organisation, partial unwinding of the helix

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8
Q

Components of protofilaments:

A

Two coiled RH helices with 3.5 residues per turn (3.6 in alpha-helices)
0.51nm pitch (0.54nm alpha helix)
21nm pitch LH supercoiling

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9
Q

What are protofibrils

A

Two pairs of coiled coils

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10
Q

How many protofibrils form each keratin microfibril?

A

Eight

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11
Q

How do cysteine residues stabilise the keratin structure?

A

They engage in cystine bridges to stabilise the structure through covalent interactions

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12
Q

What are the common residues at positions a and d?

A

Leu, Ile, Ala

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13
Q

What residues are often found in positions e and g?

A

Glu and Gly

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14
Q

What residues are often found in position g?

A

Arg and Lys

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15
Q

How does heptane organisation work?

A

A-C, C-E etc, in the heptane shape

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16
Q

What do e and g have sticking out?

A

Side chains that can be positively or negatively charged

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17
Q

Why might the heptane organisation structure have hydrophilic side chains?

A

To allow it to be in aqueous solution

Hydrophobic core

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18
Q

What is collagen a major component of?

A

Connective tissue… skin, tendons,cartilage, ligaments and bone

19
Q

What is the characteristic repeat motif of collagen?

A

-G-X-Y-

Where G is glycine

20
Q

What is type 1 collagen?

A

Type 1: tendons, ligaments, bones, two A1 chains and one a2 chain (two are the same, one is different)

21
Q

What is type 2 collagen?

A

Cartilage, three A1 chains (all three are the same)

22
Q

What is the helical pitch of collagen?

A

0.95nm (3.3 residues per turn at 0.286nm per residue)

23
Q

Why does proline prevent formation of many hydrogen bonds?

A

Proline does not have an amino group that can dissipate into hydrogen bond formation

24
Q

What role does hydroxyproline play in collagen?

A

Serves as a hydrogen bond acceptor and raises the melting temperature from 24 degrees to over 40 degrees

25
Q

Why does Gly lining the interior of the triple helix, allow for tight packing?

A

no side chains

26
Q

Where do bulkier side chains position themselves?

A

On the outer edges of the helices

27
Q

How often is a glycine reside present and why?

A

Glycine is present every third residue to allow for the tight packing (no side chains)

28
Q

What structure does tropocollagen take?

A

Triple-stranded (three separate chains) intertwined right-handed helical structure (not alpha-helical)

29
Q

What is posttranslational cross linking (modification)

A

Collagens cross-link extensively post-translation

30
Q

What does Schiff base formation create?

A

Lysinonorleucine

31
Q

What are two posttranslational modifications of collagens?

A
  • Hydroxylation of Pro and Lys

- Glycosylation

32
Q

Name four disorders associated with collagen defects?

A
  • Osteogenesis imperfecta
  • Osteoporosis
  • Ehlers-Danlos syndrome - joint hyper mobility, skin extensibility, vascular fragility
  • Familial aortic aneurism (over flexibility of major blood vessels, causing a rupture)
33
Q

Where is elastin found?

A

Arterial walls and ligaments

34
Q

What is elastin?

A

Yellow elastic connective tissue

35
Q

What is fibrillin?

A

Fibrillin is a protein from the micro fibrils, which contribute to the structure of the extracellular matrix together with collagen.

36
Q

Where are microfibrils abundant?

A

Microfibrils are abundant in skin, blood vessels, tendons

37
Q

What does fibrillin contain repeat motifs of?

A

Epidermal growth factor like modules

38
Q

How many EGF motifs does Fibrillin normally have?

A

47 EGF motifs, 43 of which bind Ca2+

39
Q

What syndrome is associated with cardiovascular and skeletal systems alongside fibrillin misfolding?

A

Marfan’s syndrome

40
Q

What is the main component of fibroid silk?

A

Glycine, then alanine

41
Q

What is the structure of fibroid?

A

Sheets, stabilised by hydrogen bonds

Side chains perpendicular to the structural plane

42
Q

What are properties of covalent structures?

A

Little elongation and provide high tensile strength

43
Q

What allows high flexibility in spidroin (spider silk)?

A

Relatively weak van der waals contacts between sheets

Structure, Function And Analysis Of Proteins (18 decks)

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