292932 collagen


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292932 collagen

  1. 1. www.Examville.com Online practice tests, live classes, tutoring, study guides Q&A, premium content and more .
  2. 2. COLLAGEN Biochemistry
  3. 3. COLLAGEN <ul><li>is the main protein of connective tissue in animals and the most abundant protein in mammals, making up about 25% of the total protein content </li></ul>
  4. 4. COLLAGEN
  5. 5. <ul><li>Collagens illustrates diverse </li></ul><ul><li>structure-function relationships </li></ul><ul><li>Collagen of tendons – forms highly asymmetric structures of high tensile strength </li></ul><ul><li>Skin collagen – forms loosely woven, flexible fibers </li></ul><ul><li>Collagen of hard regions of teeth & bone – contains hydroxyapatite, a calcium phosphate polymer </li></ul><ul><li>Collagen in the cornea – nearly crystalline, transparent </li></ul>COLLAGEN
  6. 6. <ul><li>Tropocollagen is a Triple Helical molecule </li></ul><ul><li>Rich in Gly, Pro, and Hyp </li></ul><ul><li>Tropocollagen - consist of 3 approximately 1000-residue polypeptide chains organized as left-handed non- α -helix </li></ul><ul><li>that has approximately three residues per turn. </li></ul><ul><li>Three left-handed helices entwine to form a right-handed </li></ul><ul><li>triple helix, or supercoil stabilized by hydrogen bonds </li></ul><ul><li>formed between individual polypeptide chains. </li></ul>COLLAGEN
  7. 7. Tropocollagen <ul><li>The supercoil resists unwinding because it and its three polypeptides are coiled in opposite directions. </li></ul><ul><li>The highly asymmetric mature collagen fibers measures 1.5 nm by about 300 nm, reflecting their stable, extended conformation. </li></ul>COLLAGEN Spatial arrangement of atoms. It can change only by rotating bonds, no bonds are broken.
  8. 8. α chains coiled about each other into a right-handed triple helixes
  9. 9. <ul><li>Every third residue is Glycine </li></ul><ul><li>(Gly-X-Pro/Hyp) n </li></ul><ul><li>The primary structural motif of mature collagen. </li></ul><ul><li>Every 3 rd residue is Glycine, the only residue with an R group small enough to fit within the central core of the superhelix. </li></ul><ul><li>Each Glycine is preceded by either a Prolyl or Hydroxyprolyl residue. </li></ul>COLLAGEN
  10. 10. <ul><li>Many Posttranslational modifications </li></ul><ul><li>Characterize Procollagen maturation </li></ul><ul><li>Procollagen </li></ul><ul><li>collagen precursor with the carboxyl and amino terminals have an amino acid composition typical of a globular protein. </li></ul><ul><li>During maturation of procollagen, these carboxyl and amino terminal extensions are removed by selective proteolysis. </li></ul><ul><li>Hydroxylation of prolyl and lysyl residues is catalyzed by prolyl hydroxylase and lysyl hyroxylase – enzymes that require ascorbic acid (vit. C) </li></ul><ul><li>Specific hydroxylysyl residues are then glycosylated by galactosyl and glucosyl transferases. </li></ul>COLLAGEN
  11. 11. <ul><li>Covalent cross-links stabilize collagen fibers </li></ul><ul><li>Tropocollagen associate to form collagen microfibrils. </li></ul><ul><li>Stabilized by </li></ul><ul><li>intrachain hydrogen bonds </li></ul><ul><li>Covalent bonds formed within & between helices </li></ul><ul><li>*This covalent cross-linking process involves the copper-requiring enzyme lysyl oxidase, which converts the non- α -amino groups of hydroxyl residues to aldehydes. </li></ul><ul><li>*These aldehydes then either undergo an aldol condensation or condense with the non- α -amino groups of lysine or hydroxylysine, forming Schiff bases. </li></ul>COLLAGEN
  12. 12. <ul><li>Nutritional an Genetic disorders </li></ul><ul><li>Can involve impaired secondary structure </li></ul><ul><li>The medical importance of stable secondary structures is thoroughly documented by disorders of tropocollagen biosynthesis and maturation. </li></ul>COLLAGEN
  13. 13. <ul><li>Severe Vitamin C deficiency </li></ul><ul><li>-prolyl & lysyl hydroxylases are inactive and tropocollagen cannot undergo the reactions that form covalent cross-links which results to scurv y </li></ul><ul><li>SCURVY - nutritional disorder characterized by bleeding gums, poor wound healing, an ultimately death. </li></ul><ul><li>Menke’s disease </li></ul><ul><li>is caused by a defective gene that regulates the metabolism of copper in the body. Because it is an X-linked gene, the disease primarily affects male infants. Copper accumulates at abnormally low levels in the liver and brain, but at higher than normal levels in the kidney and intestinal lining. Affected infants may be born prematurely, characterized by kinky hair and growth retardation’ </li></ul>COLLAGEN
  14. 14. <ul><li>Genetic disorders of collagen biosynthesis include several form of osteogenesis imperfecta characterized by fragile bones. </li></ul><ul><li>Ehlers-Danlos syndrome characterized by mobile joints and skin abnormalities, reflect defects in the genes that -encode α 1-procollagen, procollagen N -peptidase, or lysyly hydroxylase. </li></ul>COLLAGEN
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