Collagen Flashcards
What is the shape of fibrous proteins?
Long, rod like cylindrical shaped
Do fibrous proteins have a high or low solubility in water?
Low
What are examples of fibrous proteins?
Collagen, keratin, tropomyosin
Keratin relates to what?
Hair/nails
Tropomyosin refers to what?
Muscle
What is collagen?
Major insoluble fibrous proteins found inside extracellular matrix and connective tissue
Collagen is found in all _____ and _____ to provide framework to give tissues its form and strength.
Tissues and organs
About how much protein in your body is made up of collagen?
1/4 or 25%
How much does your skin produces collagen?
About 74%
The structure of alpha-helix is cross-linked by what?
Disulfide bonds
What are examples of alpha-helix structures?
Alpha keratin of hair, feathers and nails
What are examples of BETA conformation structures?
Silk fibroin
What are examples of collagen triple helix structures?
Collagen of tendon, bone matrix
What kind of turn is an alpha chain collagen?
Left hand turn
What kind of turn is an alpha helix?
Right hand turn
What kind of turn is a triple helix?
Right hand turn
A triple helix has 3 ____?
Identical chains
Glycine is ALWAYS positioned at what position?
3rd
How many residues/turns does collagen have?
3
How many residues/turns does alpha helix have?
3-6
In a cross section of collagen model, how is each strand bonded to other strands?
Hydrogen bonded
In a cross section of a collagen model, Glycine must appear at what space?
Every 3rd space
Where are pyrrolidone rings located in during cross section of a collagen model?
On the outside
What are the steps of Hydroxylation of Pro Residues in Pro Collagen?
Pro residue + Ketoglutarate + O2 –> 4-hydroxyprolylresidue + Succinate + CO2
What is the enzyme required for hydroxylation of pro residues in pro collagen?
Prolyl Hydroxylase and ascorbate (vitamin C)
What is collagen glycosylation?
Addition of sugar to hydroxylysine
What does the addition if sugar to hydroxylysine do?
Stabilizes the triple helix of collagen
What are the steps of the Biosynthesis of Type 1 Collagen?
- Synthesis of pro-alpha collagen
- Hydroxylation of selected prolines + lysines
- Glycosylation of selected hydroxylysines
- Self assembly of 3 pro alpha chains
- Pro collagen triple helix formation
- Secretion
- Cleavage
- Self assembly into fibril
- Aggregation of collagen fibrils to form collagen fiber
A covalent cross-linked collagen does what?
Strengthens fiber
In covalent cross-linked collagen, Lysol oxidase reaction creates ____ to react with a _____ to form a _____.
Aldehyde; lysine; schiff base
What does oxidized lysines react with to form crosslinks?
Themselves or hydroxylysine
Type I, II, and III are what type of collagen?
Fibrillar (most abundant type)
What are Type I collagen representative tissues?
- skin
- tendon
- bone
- ligaments
- dentin
- interstitial tissues
What are Type II and Type IX representative tissues?
- Cartilage
2. Viterous humor
What are type III representative tissues?
- SKIN
- MUSCLE
- BLOOD VESSELS
What type of collagen is Type IX?
Fibril associated
What type of collagen is type IV?
Sheet forming
Type IX has what kind of domain?
Fibrous and globular
What are type IV representative tissues?
All basal laminaes
What is OSTEOGENESIS IMPERFECTA?
Disease associated with collagen metabolism:
- Mutation in type 1 collagen and alpha chain
- Characterized by brittle bones
- Autosomal dominant (severe)
What is Ehlers-Danlos Syndrome?
Disease associated with collagen metabolism:
- Joint hypermobility
- Easily bruised
- Stretchable skin -> elasticity of skin
What is Scurvy?
Disease associated with collagen metabolism d/t the lack of hydroxylation of lysine and proline in collagen:
- “Liver” spots on skin
- Spongy gums, -> tooth loss
- Fingernails decay
Lysine and proline in collagen is the _____ for hydroxylation of proline (vitamin C)
Ascorbate
What are the 2 types of collagenases?
- Tissue
2. Bacterial (Clostridium Histolyticum)
Tissue collagenase:
Metalloenzymes involved in tissue remodeling or tumor invasion
Clostridium histolyticum:
Activity of toxin O involved in development of gas gangre
Collagenases also play a role in what?
- COPD (Chronic Obstructive Pulmonary Disease)
2. Cancer metastasis
Do fibrous proteins or globular proteins contain larger amounts of secondary structure?
Fibrous proteins
What type of fibrous protein structure is characterized by tough, insoluble protective structures of varying hardness and flexibility?
Alpha helix
What type of fibrous protein is characterized by soft, flexible filaments?
Beta conformation
What type of fibrous protein structure is characterized by high tensile strength, without stretch?
Collagen triple helix
Does the single strand polypeptide sequence of collagen adopt a left hand or right hand helical structure?
Left hand
In the collagen triple helix, what amino acid increases the stability b/c the side chains repel each other and extend/stretch the chain?
Proline
What amino acids that are found in collagen are absent in globular proteins?
Hydroxyproline and hydroxylysine
What characteristic of collagen structure produces the cross-striations?
A staggered alignment and cross-linking
What are the 3 hydroxylated amino acids in collagen?
4-hydroxyproline, 3-hydroxyproline, and 5-hydroxylysine
The hydroxylation of proline can’t occur in what conditions?
Anaerobic
Proline reacts with what other two substrates in the hydroxylation reaction?
Alpha ketoglutarate and Oxygen
What are the biproducts made in the hydroxylation of proline?
Succinate and CO2
What is the only amino acid that can be glycosylated in collagen?
Hydroxylysine
Glycosylation of hydroxylysine involves the addition of what two sugars?
Glucose and galactose
What organelle does the assembly of collagen fibers begin in?
ER
What sets of the biosynthesis of type I collagen occurs before the collagen can be secreted from the ER?
Procollagen triple helix formation
What amino acid is found at the C-term in collagen to initiate wrapping?
Cysteine
What enzyme is used to make the aldehydes that react with lysine to forma a Schiff base for cross-linking in collagen?
Lysol amino oxidase
Are lysine cross links more prominent in triple helical or non-triple helical regions?
Non-triple helical
Type IV collagen and laminin form what which are held together by other proteins?
Scaffolds
What is the basic unit involved in Type IV collagen?
Tetramer
The severe form of osteogenesis imperfect has what type of inheritance?
Autosomal dominant
What are the 3 important amino acids in collagen?
Proline, hydroxyproline, glycine
Which of the following is critical for proline hydroxylation?
ATP Ascorbate *** Mg2+ Gluthathione CO2
Scurvy results from the dietary deficiency of what?
Ascorbic acid