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Elastin

  • Stretchy protein within skin, lungs, large arteries, elastic ligaments, vocal cords, ligamenta flava (connect vertebrae → relaxed and stretched conformations).
  • Rich in nonhydroxylated proline, glycine, and lysine residues, vs the hydroxylated residues of collagen.
  • Tropoelastin with fibrillin scaffolding.
  • Cross-linking takes place extracellularly and gives elastin its elastic properties.
  • Broken down by elastase, which is normally inhibited by α1-antitrypsin.
    • α1-Antitrypsin deficiency results in unopposed elastase activity, which can cause emphysema.
    • Tobacco inactivates α1-antitrypsin through oxidation of a crucial methionine residue.
  • Changes with aging: ↓ dermal collagen and elastin, ↓ synthesis of collagen fibrils; crosslinking remains normal.
  • Marfan syndrome
    • Autosomal dominant connective tissue disorder affecting skeleton, heart, and eyes.
    • FBN1 gene mutation on chromosome 15 results in defective fibrillin-1, a glycoprotein that forms extracellular matrix microfibrils, which form a sheath around elastin.
    • Findings: tall with long extremities; pectus carinatum (more specific) or pectus excavatum; hypermobile joints; long, tapering fingers and toes (arachnodactyly); cystic medial necrosis of aorta; aortic incompetence and dissecting aortic aneurysms; stretch marks and lack of skin elasticity; floppy mitral valve. Subluxation of lenses, typically upward and temporally. (Look up at a ceiling fan.)
  • β-aminopropionitrile (a chemical found in certain kinds of sweet peas) causes inhibition of lysyl oxidase, an enzyme responsible for cross-linking elastin fibers and collagen fibers.  Ingestion of this compound can cause a change in the elasticity of the aorta that mimics the myxomatous degeneration seen in patients with Marfan syndrome.

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