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Applied Biochemistry > Collagen Structure and Function > Flashcards

Collagen Structure and Function Flashcards

1
Q

other ECM components are utilized in particular tissues according to other desired properties, such as (3)

A

regulation of assembly of other ECM proteins
binding of growth factors
regulation of mineralization

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2
Q

types of fibrous proteins (2)

A

structural

adhesive

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3
Q

structural fibrous porteins
provide…
examples (3)

A

provide tensile strength and elasticity

collagen, elastin, fibrillins

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4
Q

adhesive fibrous proteins
help cells…
examples (3)

A

help cells attach to ECM

fibronectin, vitronectin, laminin

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5
Q

glycosaminoglycans (GAGs)

A

long polysaccharides consisting of repeating disaccharide units

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6
Q

GAGS are often covalently linked to protein in the form of —

A

proteoglycans

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7
Q

proteoglycans form hydrated gel in which — proteins embed- resits — and aqueous phase permits — of nutrients)

A

fibrous
compression
diffusion

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8
Q

major structural component of ECM

A

collagen

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9
Q

collagen is –% of total protein mass in mammals

–% of organic material in bone, dentin

A

25%

90%

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10
Q

what kind of molecule is collagen

A

trimeric molecules consisting of three identical (homotrimeric) or non-identical (heterotrimeric) polypeptide chains (alpha chains)

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11
Q

what are collagen molecules characterized by

A

long, stiff triple stranded helical structure with 3 alpha-chains wound around each other in a rope like superhelix

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12
Q

all collagen molecules contain at least one…

A

triple helical region (collagenous domain)

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13
Q

the collagenous domain requires the presence of — every third amino acid

A

glycine

usually fly-X-Y, where X is often proline and Y is often 4-hydroxyproline

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14
Q

– different collagens identified, encoded by up to – different genes

A

28

42

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15
Q

how are collagen divided? (2)

A

fibrillar

non-fibrillar

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16
Q

polypeptide nomenclature

A

alpha chain numbering, collagen type

a1(2)

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17
Q

gene nomenclature

A

collagen type, alpha chain numbering

COL2A1

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18
Q

major fibrillar collagens (3)

A

1
2
3

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19
Q

fibrillar collagens are large collagenous domains of ~—- amino acids

A

~1000

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20
Q

assemble into higher order (polymeric) rod like structures called

A

collagen fibrils

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21
Q

molecules arranged with quarter-staggered carry gives

A

characteristic banding

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22
Q

after fibrils form, they are crosslinked between — of adjacent molecules, which

A

lysine

greatly increases tensile strength

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23
Q

type 1 collagen

A

principal collagen found in tendon, bone, ligaments, dentin, skin, (occurs in ECM as elongated fibrils)

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24
Q

type 2 collagen

A

principal collagen in cartilage matrix

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25
Q

type 3 collagen

A

(with five) important in dermal reticular fibers (small amounts in dentin)

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26
Q

type 5 collagen

A

associated with type 1 (may regulate assembly of heterotypic fibers containing type 1 and type 5)

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27
Q

type 11 collagen

A

found in cartilage, eye. helps regulate spacing/diameter of type 2 collagen fibrils

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28
Q

type 1 collagen is the major structural component of (7)

A 
bone
skin
tendon
teeth
periodontal ligament
dermis 
fasciae
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29
Q

collagen is –% of organic material in bone and teeth

A

90%

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30
Q

type 1 collagen is a heterodimer of

A

two alpha1 chains and one alpha2 chain encoded by two separate genes, COL1A1 and COL1A2

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31
Q

mutations in type 1 collagen genes (COL1A1 and COL1A2) are associated with

A

osteogenesis imperfecta

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32
Q

different variations of organization of type 1 collagen fibrils (5)

A 
parallel bundles (tendons, ligaments)
orthogonal lattices (cornea), plywood like layers
concentric weaves (bone)
wickerwork pattern, resists tensile stress in multiple directions (skin)
fibrils arranged in sailing pattern around dentinal tubules (teeth)
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33
Q

type 2 collagen is the major fibrillar collagen in (3)

A

cartilage
vitreous humor
inner ear

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34
Q

type 2 collagen is a homotrimer of..

A

alpha1 chains encoded by COL2A1 gene

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35
Q

mutations in type 2 collagen cause

A

chondrodyplasias

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36
Q

differences between non fibrillar and fibrillar collagen (3)

A

triple helical domains are shorter
interrupted by non collagenous sequences
structure is less rigid/more flexible

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37
Q

type 4 and 6 non fibrillar cartilage play an important role in

A

basal lamina

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38
Q

type 7 non fibrillar cartilage is a key component in

A

anchoring fibrils that attach epithelia to underlying connective tissue

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39
Q

type 9 non fibrillar cartilage may regulate assembly of

A

type 2 collagen fibrils

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40
Q

type 10 non fibrillar cartilage is highly expressed in

A

growth plate hypertrophic cartilage

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41
Q

steps of collagen biosynthesis/assembly (8)

A 
synthesis of pro-alpha chain 
hydroxylation of selected prolines and lysines
glycosylation of selected hydroxylysines 
self assembly of three pre-alpha chains 
pro collagen triple helix formation 
secretion
cleavage of pro peptides 
self assembly into fibril
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42
Q

primary animo acids in collagen fibers (3)

A

glycine
proline
hydroxyproline

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43
Q

hydroxylysines and hydroxyprolines are relatively rare in

A

other animal proteins

44
Q

secondary structure of collagen alpha polypeptide chains

A

extended left handed helix (collagen helix)

45
Q

proline confers 60 degree twist in molecules, which disrupts

A

other types of secondary structure from forming (ex. alpha helices, beta sheets, etc)

46
Q

each collagen helix is stabilized by

A

static revision of pyrrolidone rings of proline dn hydroxyproline residues

47
Q

collagen tertiary structure

A

no tertiary structure (3D structure of single protein molecule)
aka no folding on individual polypeptide chains due to intrachain S-S bonding, hydrophobicity, hydrogen bonding, etc

48
Q

collagen quaternary structure (3D structure of multi subunit protein)

A

three identical alpha chains wind around each other to form a right handed triple helix (3 aa residues per turn)

49
Q

For each Gly-X-Y, a hydrogen bond forms between

A

the amide hydrogen of a glycine in one chain and carbonyl oxygen of residue X in an adjacent chain

50
Q

Hydrogen bonding also occurs between OH

groups and

A

amide groups of residues in adjacent chains

51
Q

Hydrogen bonding also occurs between OH

groups and amide groups of residues in adjacent chains, which stabilizes..

A

triple helix of collagen

52
Q

Makes sense that glycine occupies every 3rd position because

A

it has the least

bulky side chain (there isn’t much room inside the triple helix)

53
Q

Because there are 3 residues per turn of the helix, every 3rd residue must
be glycine, which allows

A

three helical alpha chains to pack together to form a

triple helix

54
Q

Amino acids in X and Y positions (e.g. proline, 4-hydroxyproline) are on
the

A

outside because there is room for their bulkier side chains

55
Q

key steps in collagen biosynthesis and assembly (3)

A

post translational modifications (hydroxylation, glycosylation, intrachain disulphide bonding)
post translational modifications (proteolytic processing of pro collagen)
collagen crosslinking

56
Q

post translational modifications of collagen are important in its (2)

A

biosynthesis and assembly

57
Q

collagens undergo extensive post translational modifications in the ___ prior to triple helix formation

A

ER

58
Q

several enzymes/molecular chaperones assist in

A

trimerization and folding

59
Q

Prolyl hydroxylases and lysyl

hydroxylase –

A

hydroxylates
selected prolines and lysines
(requires vitamin C as cofactor)

60
Q

FKBP10

A

(peptidyl prolyl cis-trans
isomerase) – accelerates protein
folding

61
Q

Collagen glycosyltransfer-

ases –

A

glycosylates selected

hydroxylysines

62
Q

Protein disulphide isomerase

(PDI) –

A 
catalyzes formation of
interchain disulphide bonds
between cysteines during
nucleation of three polypeptide
chains at C-terminus
63
Q

Hsp47 –

A

chaperone protein that
binds to disulfide bonded collagen
trimers and helps complete formation
of the triple helix

64
Q

proteolytic processing of pro collagen molecules in important for — formation

A

fibril

65
Q

C-propeptides are important
in nucleation of three
collagen chains to form a

A

collagen trimer

66
Q

fibril formation only occurs after C and N propeptides are removed to form

A

tropocollagen

67
Q

collagen fibril assembly forms a — — array

A

quarter staggered

68
Q

collagen — stabilizes the fibers

A

crosslinking

69
Q

Strength of collagen fibrils greatly increased by

A

covalent

crosslinking between lysines of adjacent molecules

70
Q

key enzymes of cross linking

A

Lysol oxidases (5 identified)

71
Q

Inhibition of crosslinking (2)

A

reduces tensile strength of

fibrils/ increases tissue fragility

72
Q

Amount of cross linking increases with

A

aging

73
Q

what collagen is the major ECM component of dentin, cementum, periodontal ligament?

A

type 1 collagen

74
Q

enamel is the only calcified tissue that does not contain

A

abundant collagen

75
Q

collagen in periodontal ligament attaches

A

cementum layer of tooth root to alveolar bone

76
Q

gingiva also contains abundant collagen fibers to

A

attach gingiva to tooth and alveolar bone

77
Q

Functions of collagen fibers in the

gingiva (2)

A

− Anchoring gingival tissue to tooth/
alveolar bone
− Resisting masticatory forces

78
Q

collagen fibers in gingiva classified into

five groups

A

dentinogingival/alveogingival
circumferential
periosteal
transseptal

79
Q

Dentinogingival/Alveogingival =

A

calcified into cementum/bone at one end,
free at other end. Hold free gingiva
against tooth

80
Q

Circumferential=

A

encircle tooth

81
Q

Periosteal=

A

hold attached gingiva

against bone

82
Q

Transseptal=

A

run between teeth (not

visable in figure)

83
Q

Periodontal ligament composed

mainly of bundles of

A

type I

collagen fibrils

84
Q

PL also also contains — fibers
composed of fibrillin (provides
elasticity for tooth movement)

A

oxytalan

85
Q

Sharpey’s fibers

A

portion of fibrils anchored into

mineralized cementum or bone

86
Q

Fibrils classified into five groups

based on

A

anatomical location

87
Q

major ECM component of dentin (~90%

of organic matrix)

A

Collagen

88
Q

what collagen is mainly found in dentin

A

type 1, with trace amounts of type 3 and 5

89
Q

type 4 and 7 collagen are found in the enamel organic matrix at the

A

DEJ

90
Q

Type IV collagen restricted to

A

narrow zone at the DEJ

91
Q

Type VII collagen found in enamel organic matrix

A

adjacent to DEJ

- fibers surround enamel rods

92
Q

Type VII may play a role in attachment of enamel to

A

underlying dentin

93
Q

— — underlies all epithelial cell layers (synthesized by cells
resting on it)

A

Basal lamina

94
Q

what does the basal lamina separate

A

epithelium from underlying connective tissue stroma

95
Q

how thick is the basal lamina

A

40-120 nm thick

96
Q

In kidney glomerulus basal lamina it is important in determining which molecules will pass into

A

urine from blood (glomerular filtration)

97
Q

in skin, basal lamina is critical for attaching epidermis (epithelial outer
layer) to

A

dermis

98
Q

In oral mucosa, basal lamina is critical for attaching epithelium to

A

lamina propria

99
Q

Other roles of basal lamina in addition to structural/filtration (3)

A
  • Determining cell polarity
  • Influencing cell metabolism
  • Regulating cell survival, proliferation, migration, differentiation
100
Q

key components of the basal lamina

A

glycoproteins (laminin, nidogen)
collagens (type 4 collagen)
proteoglycans (perlecan (proteoglycan))

101
Q

here are six genes encoding type 4

collagen alpha chains –

A

COL4A1, COL4A2, COL4A3, COL4A4,

COL4A5, COL4A6

102
Q

how many different heterotrimers can be formed from type 4 collagen

A

3

α1 α1 α2) (α3 α4 α5) (α5 α5 α6

103
Q

Type VII collagen forms

A

anchoring fibrils

104
Q

Type VII collagen forms anchoring fibrils - interacts with type I collagen in stroma and type IV collagen/ laminin in basal lamina to form the

A

basement membrane

105
Q

important function in anchoring epidermis to underlying dermis or epithelium to underlying

A

stroma

106
Q

inherited disease dystrophic epidermis bullosa due to mutations in

A

COL7A1

107
Q

dystrophic epidermis bullosa

A

disease results in very fragile skin/mucous membranes that blister easily and can be sloughed off, problems with lining of the oesophagus, etc.

Applied Biochemistry (52 decks)

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