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Biochemistry (Cole) > Lecture 40 Collagen Structure and Function > Flashcards

Lecture 40 Collagen Structure and Function Flashcards

1
Q

What is the extracellular matrix?

A
  • composed from large repertoire of specialized ECM proteins with various properties assembled into an organized network/meshwork
  • often in close association with producer cells
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2
Q

What are connective tissues?

A
  • specialized tissues in which ECM is more abundant than cells
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3
Q

What is the laminal propria beneath oral epithelium composed of?

A
  • composed of collagen fibers in a connective tissue or stromal matrix
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4
Q

Teeth/bone

A
  • specialized mineralized connective tissues
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5
Q

Gingiva, peridontium

A
  • have a stromal matrix containing collagen
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6
Q

What is cartilage?

A
  • proteoglycan-rich specialized connective tissue
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7
Q

What are stroma?

A
  • cells embedded in matrix
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8
Q

What are the major components of stromal matrix?

A
  • collagen embedded in polysaccharide ground substance of hyaluronan + proteoglycans/glycosaminoglycans
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9
Q

Where are stromal cells derived from?

A
  • derived from mesodermal lineage
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10
Q

What secretes ECM in most connective tissue?

A
  • fibroblasts
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11
Q

What other cells have the capability to secrete ECM?

A
  • fibroblast related cells

- (osteoblasts, chondrocytes, odontoblasts)

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12
Q

What is the Basal Lamina?

A
  • specialized matrix at interface between connective tissue stroma and epithelium
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13
Q

What tethers lamina to underlying connective tissue?

A
  • type VII collagen anchoring fibrils
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14
Q

What is the “basement membrane”?

A
  • basal lamina combined with layer of collagen fibrils
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15
Q

How is ECM traditionally viewed?

A
  • traditionally viewed as a structurally stable material whose function is to provide support/anchorage to cells and tissues/demarcate boundaries between cells/tissues
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16
Q

ECM function in bone

A
  • support and locomotion
  • calcium homeostasis ( reservoir of calcium to be released)
  • protects brain and internal organs
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17
Q

ECM function in teeth

A
  • provides strength/structure to tooth

- resists shear and compression forces associated with chewing

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18
Q

ECM function in cartilage

A
  • support and locomotion

- resilient - shock absorber for compressive forces associated with locomotion, mastication

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19
Q

`ECM roles in addition to structural roles

A
  • Embryonic development (cell adhesion/migration/tissue morphogenesis)
  • Regulation of Cell function (signaling/ growth/ differentiation)
  • Tissue repair/ wound healing
  • Angiogenesis
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20
Q

How does the composition of ECM change in each tissue?

A
  • perfectly suited to biomechanical/functional requirements of the tissue
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21
Q

How is ECM viewed as composite material?

A
  • various building materials (macromolecules) with different mechanical properties combined/organized to create a tissue with optimal mechanical properties
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22
Q

What encodes for the components of ECM?

A
  • genes
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23
Q

what is the EcM like in the bone and teeth?

A
  • calcified hard ECM
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24
Q

What is the ECM like in the cornea?

A
  • optically transparent ECM
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25
Q

What is the composition of ECM in tendons?

A
  • rope-like organization of collagen gives tensile strength in one direction
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26
Q

What is the property of collagen (fibrillar)?

A
  • tensile strength
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27
Q

What is the property of proteoglycans?

A
  • resilience/resistance to compression
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28
Q

What is the property of elastin?

A
  • elasticity/resilience
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29
Q

What is the property of Fibrillin-1 (microfibrils)?

A
  • controlled elasticity
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30
Q

What is the property of the mineral hydroxyapatite?

A
  • strength, hardness, but also brittleness
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31
Q

What are the major macromolecules of the ECM?

A
  • Fibrous proteins

- Glycosaminoglycans (GAGs)

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32
Q

What are the structural fibrous proteins?

A
  • collagen, elastin, fibrillins

provide tensile strength, elasticity, etc.

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33
Q

What are the adhesive fibrous proteins?

A
  • fibronection, vitronectin, laminin
    (help cells attach to ECM)
    (have receptors on cell surface)
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34
Q

______ are long polysaccharides consisting of repeating disaccharide units often covalently linked to protein in the form of proteoglycans (form hydrated gel in which fibrous proteins embed- resists compression and aqueous phase permits diffusion of nutrients etc)

A
  • Glycosaminoglycans (GAGs)
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35
Q

_____ is the major structural component of ECM (25% of total protein mass in mammals) (90% of organic material in bone, dentin)

A
  • collagen
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36
Q

How many chains does collagen consist of?

A
  • 3 poly peptide chains (alpha chains)
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37
Q

Are the collagen chains homotrimeric or heterotrimeric

A
  • they can be either
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38
Q

T/F all collagen molecules contain at least one triple helical region (collagenous domain) - requires presence of glycine every third amino acid ( usually gly-X-Y where X is often proline and Y is often 4-hydroxyproline)

A
  • True
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39
Q

Is type 2 collagen a homo or hetero trimer?

A
  • homo trimer that has 3 alpha 1 chains
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40
Q

is type 1 collagen a homo or hetero trimer?

A
  • its a hetero trimer with 2 alpha 1 chains and one alpha 2 chains
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41
Q

What chains make up type 6 collagen?

A
  • alpha 1, 2, and 3

- type 6 is heterotrimer

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42
Q

What type of collagen assembles into higher order rod-like structures?

A
  • fibrillar collagens
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43
Q

What are the fibrillar collagens?

A
  • 1
  • 2
  • 3
  • 5
  • 11
  • 24
  • 27
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44
Q

What are the major fibrillar collagens?

A

I, II, III

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45
Q

After fibrils form they are ________ between lysines of adjacent molecules (greatly increases tensile strength)

A
  • Crosslinked
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46
Q

What gives fibrillar collagen its characteristic banding?

A
  • the molecules are arranged with quarter- staggered array
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47
Q

What is the principle collagen found in tendon, bone, ligaments, dentin, skin

A
  • Type I

occurs in ECM as elongated fibrils

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48
Q

T/F Functions of Fibrillar collagens are relevant to craniofacial biology

A
  • T
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49
Q

What is the principle collagen in cartilage matrix?

A
  • type II
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50
Q

What type of collagen (with V) is important in dermal reticular fibers (small amounts in dentin)

A
  • type 3
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51
Q

What type of collagen is associated with type I (may regulate assembly of heterotypic fibers containing type I and type V)?

A
  • type V
52
Q

What type of collagen is found in cartilage, eye, and helps regulate spacing/diameter of type II collagen fibrils

A
  • type XI
53
Q

What is the major structural component of bone, skin, tendon, teeth, periodontal ligament, dermis, and fasciae?

A
  • type I collagen
54
Q

What makes up 90% of organic material in bone and teeth?

A
  • type I collagen
55
Q

What types of chains make up Type I collagen?

A
  • heterotrimer of two alpha i chains and one alpha 2 chain encoded by genes COL1A1 and COL1A2
56
Q

What do mutations in type 1 collagen genes lead to?

A
  • osteogenesis imperfecta
57
Q

How are the type 1 collagen fibers in the tendons/ligaments arranged?

A
  • parallel bundles
58
Q

How are the collagen of the cornea arranged?

A
  • orthogonal lattices (ply-wood like layers)

- this is transparent so you can see

59
Q

What is the arrangement of type 1 collagen in bone?

A
  • concentric weaves
60
Q

Why is the collagen of the skin arranged in wickerwork pattern?

A
  • resists tensile stress in multiple directions
61
Q

How is the collagen in the teeth arranged?

A
  • fibrils arranged in a swirling pattern around dentinal tubules
62
Q

What is the major fibrillar collagen in cartilage, vitreous humor, and inner ear?

A
  • type II collagen
63
Q

What is the chain composition of type II collagen?

A
  • homotrimer of two alpha 1 chains encoded by COL2A1
64
Q

What do mutations in type II collagen cause?

A
  • chondroplasias
65
Q

What are the non fibrillar collagens?

A
  • IV, VI-X, XII- XXIII, XXV, XXVI, XXVIII
66
Q

How are non fibrillar collagens arranged?

A
  • they are triple helical domains that are shorter, interrupted by non-collagenous sequences ->
  • structure is less rigid and more flexibile
67
Q

What non fibrillar collagens have an important role in basement membrane?

A
  • IV and VI
68
Q

What no fibrillar collagen is a key component of anchoring fibrils that attach epithelia to underlying connective tissue

A
  • type VII
69
Q

What collagen may regulate assembly of type II collagen fibrils?

A
  • type IX
70
Q

What collagen is highly expressed in growth plate hypertrophic cartilage?

A
  • type X
71
Q

_______ is the major ECM component of Dentin, Cementum, and Peridontal ligament

A
  • Type I collagen
72
Q

_______ is the only calcified tissue that does not contain abundant collagen?

A
  • Enamel
73
Q

Collagen in the ______ attaches cementum layer of tooth root to alveolar bone

A
  • peridontal ligament
74
Q

_____ also contains abundant collagen fibers to attach gingiva to tooth and alveolar bone

A
  • Gingiva
75
Q

What are the functions of collagen fibers in the gingiva?

A
  • anchoring gingival tissue to tooth/alveolar bone

- resisting masticatory forces

76
Q

______ collagen fibers are calcified into cementum/bone at one end and free at the other end, and hold free gingiva against the tooth

A
  • Dentinogingival/ Alveogingival
77
Q

________ encircle the tooth

A
  • circumferential collagen fibers
78
Q

_____ hold attached gingiva against bone

A
  • periosteal
79
Q

_____ run between teeth

A
  • transseptal
80
Q

What type of collagen fibrils is the peridontal ligament primarily composed of?

A
  • Type I
81
Q

What provides elasticity in the periodontal ligament for tooth movement?

A
  • oxytalan fibers composed of fibrillin
82
Q

What are the portion of fibrils anchored into mineralized cementum or bone?

A
  • sharpeys fibers
83
Q

What is the major ECM. component of dentin?

A
  • collagen (mainly type I with trace amounts of type III and V)
  • (90% of organic matrix)
84
Q

What collagen is found at the DEJ?

A
  • type IV
85
Q

what collagen has been found at the DEJ that extends into enamel?

A
  • type VII
86
Q

What collagen might play a role in attachment of enamel to underlying dentin?

A
  • type VII
87
Q

Type ____ collagen is important in the basal lamina?

A
  • Type IV
88
Q

_____ underlies all epithelial cell layers and is synthesized by cells resting on it

A
  • Basal lamina
89
Q

What separates epithelium from underlying connective tissue stroma?

A
  • Basal lamina
90
Q

What is the function of the basal lamina in the kidney glomerulus?

A
  • important in determining which molecules will pass into urine from blood (glomerular filtration) 🩸
91
Q

What is the function of the basal lamina in the skin?

A
  • critical for attaching epidermis (epithelial outer layer) to dermis
92
Q

What is the function of basal lamina in the oral mucosa?

A
  • critical for attaching epithelium to lamina propria
93
Q

What are some of the other roles of basal lamina in addition to structural/filtration?

A
  • determining cell polarity
  • influencing cell metabolism
  • regulating cell survival, proliferation, migration, differentiation
94
Q

What are the key components of the basal lamina?

A
  • glycoproteins
  • collagens
  • proteoglycans
95
Q

What glycoproteins are in basal lamina?

A
  • laminins (primary component/main organizer)

- nidogen

96
Q

What collagens are found in basal lamina?

A
  • type IV collagen (provides tensile strength)

- type VI collagen (at stromal interface)

97
Q

What proteoglycans are in basal lamina?

A
  • perlecan (proteoglycan)
98
Q

Notes about type IV collagen

A
  • 6 genes encode for it
  • three different hetero trimers can be formed
  • this complexity helps the basement membrane have different properties
99
Q

Type _____ collagen is important in anchoring the epidermis to the underlying dermis

A
  • VII
100
Q

Type VII collagen forms ________ interacts with type I collagen in stroma and type IV collagen/laminin in basal lamina (together called basement membrane)

A
  • anchoring fibrils
101
Q

The basement membrane is?

A
  • type VII collagen with basal lamina
102
Q

What inherited disease is due to mutations in COL7A1?

A
  • dystrophic epidermis bullosa
103
Q

What collagen has an important function in anchoring epidermis to underlying dermis or epithelium to underlying stroma?

A
  • Type VII
104
Q

Dystrophic epidermis bullosa results in?

A
  • very fragile skin/mucous membranes that blister easily and can be sloughed off, problems with lining of esophagus, etc.
105
Q

What are the steps of collagen biosynthesis?

A
  1. Synthesis of PRO- alpha chain
  2. Hydroxylation of slected prolines and lysines
  3. Glycosylation of selected hydroxylysines
  4. Slef assembly of three pro alpha chains (C terminal ends bind together)
  5. procollagen triple helix formation
  6. secretion
  7. Cleavage of proppeptides
  8. self assembly into fibril
  9. aggregation of collagen fibrils to form a collagen fiber
106
Q

Why is collagen high in glycine?

A
  • located at very 3rd residue and allows the collagen to pack tightly
107
Q

In gly-X-y repeating motif the X is what and Y is?

A
  • proline and

- 4-hydroxyproline

108
Q

Does collagen have a tertiary structure?

A
  • nope
109
Q

What makes up the quaternatery structure of collagen?

A
  • three helical chains wind around each other to form a right handed triple helix
110
Q

What stabilizes the triple helix of collagen?

A
  • hydrogen bonding between amide hydrogen of glycine in one chain and carbonly oxygen residue x in an adjacent chain
  • hydrogen bonding also occurs between OH groups and amide groups of residues in adjacent chains
111
Q

What is the secondary structure of collagen alpha polypeptide chains?

A
  • extended LEFT handed helix (collagen helix)
112
Q

What stabilizes each collagen helix?

A
  • static repulsion of pyrrolidone rings of proline and hydroxyproline residues
113
Q

Proline confers ____ twist in molecule which disrupts other types of secondary structure from forming (e.g. alpha helices, beta sheets)

A
  • 60 degree twist
114
Q

Why does the glycine occupy every 3rd postion?

A
  • least bulky side chain

- allows three helical alpha chains to pack together to form a triple helix

115
Q

Amino acids X and Y (proline, 4-hydroxyproline) are located where?

A
  • outside so there is room for their bulkier side chains
116
Q

Prolyl hydroxylases and lysyl hydroxylase

A
  • hydroxylates selected prolines and lysines

requires vitamin C as a cofactor

117
Q

FKBP10

A
  • accelerates protein folding
118
Q

Collagen glycosyltranferases

A
  • glycosylates selected hydroxylysines
119
Q

Protein disulphid isomerase (PDI)

A
  • catalyzes formation of interchain disulphide bonds between cysteines during nucleation of three polypeptide chains at C-terminus
120
Q

Hsp47

A

Chaperone protein that binds to disulfied bonded collagen trimers and helps complete formation of triple helix

121
Q

What are the C-propeptides important in procollagen processing?

A
  • important in nucleation of 3 collagen chains to form collagen trimer
  • but fibril formation only occurs after C and N pro peptides are removed to form tropocollagen
122
Q

What is responsible for cleaving off N-propeptide?

A
  • AdamsTS2
123
Q

What is responsible for cleaving off C-propeptied?

A
  • BMP-1/tolloid proteinases
124
Q

What enzyme is important in collagen crosslinking?

A
  • lysyl oxidases
125
Q

What increases tissue fragility in collagen?

A
  • inhibition of crosslinking

- also reduces tensile strength of fibrils

126
Q

What greatly increases the strength of collagen fibrils?

A
  • covalent crosslinking between lysines of adjacent molecules
127
Q

T/F amount of cross linking increases with aging

A
  • T

Biochemistry (Cole) (25 decks)

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