rational drug design

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rational drug design
2010-06-06 18:58:45

Rational drug design
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  1. Oxytocin
    • Nonapeptide hormone
    • Acts as brain neurotransmitter
    • Released during labour and facilitates birth and breastfeeding
    • Mol wt: ca. 1000
    • Must be given as injection or nasal spray
    • Used to induce labour in difficult pregnancies
  2. Cyclosporin
    • Immunosuppressant
    • Used in organ transplant operations to reduce risk of rejection
    • Initially isolated from soil fungus
    • Mol wt ca.1200
    • Cyclosporin A (main form) cyclic 11 aa peptide
  3. Hep B vaccine
    • Protein or peptide fragments from the pathogen (rather than inactivated or attenuated microorgs)
    • Consists of hepatitis B surface antigen (HBsAg) protein of the virus which is cloned and expressed at very high levels in yeast cells
    • Creates immune response which leads to immunity
  4. Factor VII
    • Blood clotting factor
    • Defects in this gene result in haemophilia A (common recessive X-linked coagulation disorder)
    • Cofactor for factor IXa which forms a complex which converts factor X to the activated Xa
    • Mol wt ca. 80000 Da (roughly 800 aa)
  5. Factor X
    • Thrombokinase
    • Coagulation cascade
    • Active form has an endopeptidase function
    • Synthesised in the liver (using Vit K)
    • First member of the thrombin pathway
    • Xa cleaves prothrombin in two places which yields active thrombin
    • Mol wt ca. 55,000
  6. Alpha 1-antitrypsin
    • Glycoprotein
    • Serine protease inhibitor
    • Protects lung and liver tissue from damage
    • If absent it results in repiratory complications
    • Used in the treatment of emphysema or COPD
  7. What is the problem with sourcing therapeutic proteins from animal sources
    • The proteins tend to be potent and therefore are produced in minute quantities in the human body
    • Similar for animal tissue, it can be totally unproductive to produce the protein in the way
    • e.g. somatostatins inital isolation (50's) required 1/2 million sheep brains to be homogenised to extract 5mg of protein
    • rDNA technology can now produce that amount from 5L of transformed E.coli
  8. Somatostatin
    • Growth hormone inhibiting hormone (GHIH)
    • Reguates endocrine system and affects cell proliferation and growth
    • Works through interaction with somatostatin receptors
    • Poorly absorbed from the gut - s.c. injection
    • Treats carcinoid syndrome and acromegaly
    • Two active forms, one of 14 aa, the other 28
  9. Recombinant DNA technology
    • Allows proteins to be produced;
    • in large amounts
    • at a fraction of the cost
    • without the use of animals

    Also allows the production of novel compounds
  10. What is rDNA technology
    rDNA technology involves the addition, removal or alteration of genetic material within a cell

    A DNA molecule is said to be recombinant when it is composed of DNA segments from more than one species

    it involves cloning the desired gene into some sort of host cell e.g. E.coli
  11. Advantages and disadvantages of E.coli in rDNA technology
    • Advantages:
    • Ease of manipulation
    • Many expression vectors available
    • Cheap and easy to culture

    • Disadvantages:
    • Don't get export of proteins to medium
    • Proteins may form inclusion bodies
    • Proteins may be rapidly degraded
    • No post translational modification
  12. Advantages and disadvantages of Saccharomyces cerevisiae in rDNA technology
    • Advantages:
    • Widely used industrial organism
    • Cheap and easy to culture
    • Glycosylates proteins
    • Can get export of proteins into media
    • Good expression systems available

    • Disadvantages:
    • Post-translational modifications may not be the same as those in human cells
  13. Advantages and disadvantages of mammalian cells in rDNA technology
    • Advantages:
    • Get export of proteins into media
    • Get the desired post-translational modifications
    • Good expression systems available
    • Unlikely to be immunogenic to humans

    • Disadvantages
    • Difficult and expensive to culture
    • Great care needed to avoid contamination of cultures
  14. Post translational modifications of proteins
    • Proteolytic processin
    • N and O linked glycosylation
    • Amidation, sulphation
    • Phosphorylation
    • Attachment of fatty acids