collagen synth/connective tissue diseases
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Type I, II, III, and IV collagen is found in which tissues?
I: skin, bone, tendon, vasculature, cornea (mechanical stability, resistance to tension)
II: cartilage, vitreous-body, vertebral disk (tensile strength)
III: vasculature, organs, skin (flexibility)
IV: basement membrane (support)
Collagen chain repeat consists of?
Gly-X-Y (X = proline, Y = hydroxylproline, hydroxylsine)
Each collagen chain forms a ____-handed helix bit the landmark structure forms a ____-handed helix from h-bonding
synthesized in RER as ____ and signal peptide is cleaved to make _____
pre-pro-alpha chain; pro-collagen
What do prolyl and lysyl-hydroxylase + ascorbate do?
- In RER, hydroxylproline and hydroxylysine are produced via these enzymes (this is UNIQUE to collagen)
Hydroxylysine on the end chains of pro-peptide are _______ to add _____ or ____ which increases turnover rate.
O-glycosylated; galactose or glucosyl-galactose
Intermolecular di-sulfide bonds are formed by? Where are these bonds formed? Intracellularly or extracellularly?Purpose?
- protein disulfide isomerase (oxidates cystein residues);
- in C-terminus extension;
- Within the cell;
- permit H-bonding and triple helix formation
Procollagen peptidases do what?
cleace N, C termini extensions to give tropocollagen which associate in parallel array 3/4 length overlap
What fills the gap regions of 3/4 length overlap of tropocollagen fibrils?
CaPO4 in bone formation
what does lysyl-oxidase do? Why?
oxidatively deaminates hydroxylysyl and lysyl residues to form aldehydes (allysine/hydroxyallysine)
aldehydes of adjacent tropocollagens stabilze fibrils (via condensation)
In biosynthesis of collagen, where does each step occur?
- 1. removal of pre-peptide (i.e. signal peptide)
- 2. hydroxylate pro/lys residues via prolyl or lysyl-hydroxylase (i.e. cytosolic enzymes)
- 3. glycosylate hydroxylysine on end chain
- 4. oxidation of cys (i.e. formation of S-S bonds)
- 5. assembly of 3 peptides to form triple helix
- Extracellular:6. removal of the pro-peptide (i.e. N,C extensions)
- 7. staggered (3/4 length overlap) to form fibrils
- 8. gap junctions filled with CaPO4
- 9. Oxidation of hydroxylysyl and lysine residues to aldehyde form
Different types of Ehler's-Danlos syndrome?
Stretchy skin and loose joints.
group of disorders in which bone bends and easily fracture due to defective collagen 1 resulting from mutation in the collagen repeat that prevents helix formation (i.e. gly for bulky amino acid)
vit. c deficiency prevents hydroxylation of pro/lys residues such that h-bonding cannot occur in pro-collagen
NOT a collagen based disease. It's elastin (or fibrillin) based.
caused by mutation in fibrillin gene
long fingers, arms, legs
platelets bind to type IV collagen on basal lamina
breast tumors where proliferation of fibroblasts continue to lay down type I collagen to make tumor palpale
tumors enter blood stream
elastin has ___-like qualities and found in?
Elastin is hydro phobic or philic?
hydrophobic and contains small, non-polar AA (GAV)
Elastin cross-links into irregular networks by which AA?
short stretches of Lysine, X, Y (X=y=non polar AA like alanine)
unique 4-residue cross-links of elastin; uses lysyl oxidase (creates allysel residues)
elastin fibers covered with glycoproteins
elastin vs. collagen in:
turn over rate and genes that create them? Shared enzymes?
- elastin is most stable protein in body (slowly turned over)
- elastin is made from ONE gene; collagen from many genes
shared enzyme: lysyl oxidase
What are GAGs?
large, unbrached neg. charged polysaccharide chains associated with protein core
How do GAGs attach to protein core?
protein core (ser or thr) attached to linker tri-sacc. (Gal-Gal-Xyl) which is attached to acidic sugar (negative)-amino sugar (neutral) repeat.
*negative charges allow sacc. chains to repel each other (looks like test tube cleaner)
PG reacting with hyaluronic acid to create this. Can absorb compressive forces, spring back b/c of neg. charges
**allows for flexibility/compressibility of collagen fibers (ear)
GAGs lubricating properties are related to mucous secretions and prevalent in ____?
cartilage and synovial fluid
dynamic remodeling of connective tissue is indicative by?
increased detection of hydroxylysin/hydroxylproline in ruine 2 days after exercise
lysosomal storage disease?
lysosomes hold many acid hydrolases that degrade GAGs..many deficiences are characterized by missing one or more enzyme required to degrade GAGs
how can you test lysosomal storage diseases?
check urine for presence of characteristic oligosaccharides
Fibronectin? Vitronectin? Laminin?
fibronectin: group of proteins that interact with cell surface proteins (integrins)
vitronectin: fibronectin in localized areas of tissue injury
laminin: attach to basal lamina
**cell adhesion to fibronectin/laminin can promote growth, migration
where does proteoglycan synthesis occur (in or out of cell)?
In cell (RER --> golgi)
What are the six proteoglycans?
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