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Collagen (Synthesis (2) Hydroxylation (cofactors (Vitamin C/Ascorbic Acid,…
Collagen
Synthesis
1) Pro-alpha chain synthesis
Alpha 1/Alpha 2 mRNA Synthesized
Translation by ribosome
secretion into RER
2) Hydroxylation
effected by
lysyl hydroxylase
prolyl hydroxylase
cofactors
Vitamin C/Ascorbic Acid
Ferrous Iron (Fe2+)
Molecular Oxygen
3) Glycosylation
occurs to
hydroxylysine
4) Procollagen formation
occurs when
three pro-alpha chains form triple helix
C-terminal propeptide forms disulfide bonds
N-terminal propeptide forms disulfide bonds
5) Secretion
Golgi Apparatus secretes procollagen
6) Extracellular Clevage
cleaved by
N-procollagen peptidase
C-procollagen peptidase
7) Collagen Assembly
Tropocollagen forms staggered fibril spontaneously
8) Cross-linking
caused by
lysyl oxidase
which targets
lysine and hydroxylysine residues
Structure
Primary Structure
Repeating Tetromere
composed of
Glycine
Proline/Hydroxylproline
Lysine/Hydroxylysine
Secondary Structure
Hydrogen Bonding
facilitated by
Hydroxylproline
Hydroxylysine
Tertiary Structure
Triple Helix of Chains
Alpha 1
Alpha 2
Types
Fibril Forming
Type 4
Located in
Extracellular Membrane
Type 8
Located in
Corneal and Vascular endothelium
Network Forming
Type 9
Located in
Cartilage
Type 12
Located in
Tendons and Ligaments
Fibril Associated
Type 1
Located in
Ligaments
Tendons
Cornea
Type 2
Located in
Cartilage
Type 3
Located in
Blood Vessels
Skin
Muscle
Collagenopathies
Ehlers-Danlos syndrome
Types
Typical
causes
skin extensibility
skin fragility
joint hypermobility
Vascular
causes
aortic rupture
caused by
heritable defects in processing enzymes or mutations in AA sequence
Osteogenesis imperfecta
Types
Type 1
causes
mild bone fragility
hearing loss
blue sclerae
Type 2
causes
fetal demise d/t pulmonary complications
broken bones in utero
Type 3
causes
fractures at birth
short stature
spinal curvature
blue sclerae
caused by
mutations in AA sequence for alpha chains