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Collagens and Disorders
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- 1Synthesised intracellular and mature extracellular, associate with ECM and minerals to form CT (fibrillar). Only protein with amino acid sequence. Non fibrillar in basement membrane and ECM and non collagen collagens. Single helix, left but triple, right (tensile strength)Repeat of guy important as only aa small enough to fit in central helix core, less tight than a helix.
Hydroxyproline for stability (no genetic code)
Hydroxylysine (same) essential for glycosylation, affects cross link formation, water retention and flexibility. - 2Hydroxylation of proline and lysine are mixed function oxidases, in RER, require iron, ascorbic acid (keeps Fe2+ in reduced form - active) and 2-oxoglutarateGlycosylation - addition of galactosyl and glucose residues to hydroxylysine.
In helix formation, inter-chain S-S start at C terminus (so mutations worse at this end), forms C -> N
Trim ends of helix so packages nicely, by N-peptidase and C-peptidase - 3ProcollagenHelix formation speed crucial, delay results in over modification and becomes unstable
Pro and lys hydroxylases and glycoslases active on non-helical substrate only
Helix assemble in RER and modification in golgi, converted into tropocollagem by trimming ends. - 4Lysine oxidaseDeaminates some lysine amino groups to form -CHO, aldehyde, very reactive and forms links with other lysine amino and -CHO groups on adjacent tropocollagens.
- 5StriationsMature collagen means fibril alignment (in bone fibres at right angles)
Striations staggered as if in same place would form areas of weakness - 6Vitamin C Defiency Scurvy EnvironmentalCollagen under-hydroyltaed (proper helices do not form), accumulate in cells, unstable, skin bruises easily from capillary haemorrhages, gums and GI bleed
- 7Copper Deficiency EnvironmentalNeeded for activity of lysine oxidase (Cu is co-factor)
Inability to absorb copper, leads to defective cross links - 8Lathyrism EnvironmentalAfter eating sweet pea seeds
Contain competitive inhibitors of lysine oxidase, collagen has defective cross links - 9Osteogenesis imperfecta GeneticType I disorder, autosomal dominant
Brittle bones, near C more severe, gly substiution - 10Ehlers-Danlos Syndrome GeneticHeterogenous, autosomal recessive/dominant/X-linked
Hyper extensible skin and hypermobile joints
Bad wound healing - 11Epidermolysis bullosa GeneticSevere blistering, from mutation
- 12Chondrodystrophies GeneticAffect formation and function of growth plate cartilage
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- Fichas sobre Collagens and Disorders, creado por maryamnc el 04/01/2015.
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