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Molecules and Cells Unit 1A > Proteins IV > Flashcards

Proteins IV Flashcards

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Organic Chemistry 101 flashcards
1
Q

What is the secondary structural unit in collagen?

A

Polyproline Type II-like helix

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2
Q

Which Ehlers-Danlos Syndrome (EDS) is associated with a type I collagen mutation.

A

Arthrochalasis

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3
Q

What two fibrous proteins exist as dimers (and rarely trimers) of right-handed alpha helical chains?

A

alpha-Keratin and tropomyosin

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4
Q

How are alpha-keratin and tropomyosin arranged around each other?

A

parallel and coil about each other in a left-handed super twist

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5
Q

What protein is appropriate for hydrophobic packing to stabilize the force for the tropocollagen helix?

A

Glycine (its the only aa small enough)

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6
Q

ALL collagen has an extensive, repeated tripeptide sequence “Gly-X-Y”. What are “X” and “Y” usually?

A

Proline and Hydroxyproline respectively

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7
Q

Kyphoscoliosis EDS is due to a mutation in the gene for

A

Lysyl Hydroxylase

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8
Q

What is the functional unit of collagen?

A

Tropocollagen

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9
Q

How are individual collagen polypeptide chains in tropocollagen stabilized?

A

Via H-bonds between the amino terminus-glycine residue and the carboxy terminus-proline (or hydroxyproline) residue.

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10
Q

What dictates the antigen Ig will bind to?

A

The Hyper-variable Regions (Complementarity Determining Regions) on the heavy and light variable chains of Immunoglobulins.

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11
Q

What is the collagen content (percentage) in the skin?

Where in the body is collagen content the lowest?

A
  • 74%

- liver (4%)

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12
Q

Osteogenesis imperfecta is an autosomal dominant disorder associated with what type of collagen mutation? What gene location does this occur at?

A
  • Type I collagen

- alpha (I) chain

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13
Q

What enzymatic process must occur to prevent vessels, skin, and tendons from becoming fragile?

A

Hydroxylation of proline in procollagen formation

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14
Q

In the formation of collagen, what molecules are organized into bundles called fibrils? What occurs following this collagen formation step?

A
  • Tropocollagen

- cross-linkage to form fibers

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15
Q

What individual regions are created by the cleavage done by papain?

A

2 Fab (antigen-binding fragment) and 1 Fc (fragment crystallization)

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16
Q

What region of papain does cleavage take place at?

A

The hinge region (between CH1 and CH2 of both heavy chains)

*CH = Constant Heavy chain

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17
Q

What is the fundamental tertiary structural element of antibodies?

A

The Ig Fold

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18
Q

What region of an antibody participates in antigen-binding?

A

The loops containing HVR/CDRs

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19
Q

During fibrillar collagen formation, what oligosaccharide-linked amino acid is added to the C-terminal of procollagen?

A

Asparagine (Asn)

20
Q

Aggregation of antigens is possible due to what two factors?

A

1) Antigens posses multiple antigenic determining reasons

2) Antibody bivalency

21
Q

Name the key modification products of Lysine/hydroxylysine residues

A

1) Allysine
2) Hydroxyallysine
3) Lysinorleucine
4) Aldol Crosslink

22
Q

What is the key enzyme (and its cofactor) involved in tropocollagen fibril cross-linking?

A
  • Lysyl-amino oxidase

- Cu2+

23
Q

What gives fibrils a striated appearance in an electron micrograph?

A

The 67 nanometer staggering of trimers

24
Q

What are the components of the basal lamina?

A

The collagen layer:

  • type IV collagen
  • Nidogen/entactin

The Laminin layer:

  • laminin
  • perlecan
25
Q

What syndrome is caused by faulty synthesis of collagen?

A

Ehler’s-Danlos Syndrome (EDS)

26
Q

Name the 6 major types of Ehler’s-Danlos Syndrome?

A 
Type 1 - Hyper-mobility 
Type 2 - Classic
Typer 3 - Vascular
Type 4 - Arthrochalasis
Type 5 - Kyphoscoliosis
Type 6 - Dermatosparaxis
27
Q

Where is the hydrophobic stripe formed between alpha-keratin and tropomyosin? What is the purpose of this stripe formation?

A
  • Between residues “a” and “d” in the a-g heptad

- Stabilizes the coil-coiled structure

28
Q

Where do interchain salt bridges form between alpha-keratin and tropomyosin?

A
  • Between residues “e” and “g”

* these should be charged aa’s

29
Q

What fibrous proteins have the possibility of forming both homo and hetero-dimers and trimers?

A

Alpha-keratin and tropomyosin

30
Q

Compare and contrast the residues/turn and pitch of an alpha helix vs a polyproline type II helix, as well as its coil structure.

A

3.3 residues/turn (3.6 for α-helix)
9.4 Å pitch (5.4 Å for α-helix)
Left-handed coil (α-helix is usually right-handed)

31
Q

In the hydroxylation of proline, what cofactors are required for prolyl hydroxylase function?

A
  • Ascorbate (Vit C)

- Fe2+

32
Q

What collagen type are the basement membrane and lens capsule composed of?

A

Type IV

33
Q

Type IV collagen only contains small amounts of which two amino acids?

A

Alanine (Ala, A) and Arginine (Arg, R)

34
Q

What percent carbohydrate content is type IV collagen?

A

15%

35
Q

Good Pasture’s syndrome is a hypersensitivity reaction to antigens in the non-collagenous domain of what collagen type/chain gene?

A

Type IV/alpha(3) chain

36
Q

What organs does Good Pasture’s Syndrome affect?

A

The glomerulus and pulmonary alveoli

37
Q

What is the purpose of the frequently appearing proline and hydroxyprolines in the polyproline structure?

A

Minimization of steric clash between pyrrolidine side-chain and peptide backbone.

38
Q

What may cause Hypermobility (Type 1) EDS

A
  • joint dislocation
  • type III collagen mutation
  • tenascin-X mutation
39
Q

Which EDS is the most rare and what is its mutation?

A

Vascular (type III)

40
Q

How many loops define an antigen binding site?

A

-6

41
Q

How many antigen binding sites are there per Ig fold?

A

-3

42
Q

Which fibrous protein is abundant in ligaments, the lungs, and skin?

A

Elastin

43
Q

What lysine modification does elastin form crosslinks with?

A

Allysine

44
Q

Which chaperone protein binds to helices in collagen and what is the outcome of this binding?

A
  • Hsp47 (Heat Shock Protein)

- prevents premature aggregation

45
Q

What reaction do Nitrogen and Carbon proteinases (Bone Morphogenic protein) catalyze?

A

The removal of N & C terminal propeptides

Molecules and Cells Unit 1A (11 decks)

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