A QUICK GLANCE AT PROTEIN STRUCTURE

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A QUICK GLANCE AT PROTEIN STRUCTURE

  1. 1. Understanding Protein Structure Gabrielle Roberts Biology Department, Long Island University, Brooklyn, NY
  2. 2. Introduction <ul><li>I. Overview: What is a Protein? </li></ul><ul><li>II. Basic Protein Structure </li></ul><ul><li>-The Amino acid </li></ul><ul><li>-Primary structure: Polypeptide </li></ul><ul><li>III. Protein Folding Patterns: </li></ul><ul><li>Secondary, Tertiary, Quaternary </li></ul>
  3. 3. PROTEINS <ul><li>Proteins are biological molecules which play important structural and functional roles within living organisms </li></ul>
  4. 4. <ul><li>FUNCTIONAL PROTEINS </li></ul><ul><li>Carry out the vital functions of living systems: chemical reactions, transport, signaling, etc. </li></ul>
  5. 5. Chemical Reactions: Enzymes Cell Signaling: Hormones Transport: Red Blood cells Immunity: Antibodies
  6. 6. <ul><li>STRUCTURAL PROTEINS </li></ul><ul><li>-Provide strength and support </li></ul>
  7. 7. Muscle Tissues: Actin and Myosin Hair & Nails: Keratin Cytoskeleton: Microtubules, intermediate filaments, microfilaments Collagen “fibrous protein”: bones, tendons,
  8. 8. Basic Protein Structure <ul><li>Each protein starts with a basic amino acid chemical structure: </li></ul><ul><li>- Amino group </li></ul><ul><li>- Carboxylic acid group </li></ul><ul><li>- Variable R group </li></ul><ul><li>“ side chain” </li></ul><ul><li>R groups give amino acid their special chemical and physical properties </li></ul>
  9. 10. Polypeptide formation <ul><li>Amino acids combine through a dehydration reaction. The result is the formation of a peptide bond. </li></ul>
  10. 11. <ul><li>Oligo peptide- less than 30-50 amino acids </li></ul><ul><li>A Polypeptide is a chain of more than 50 amino acids </li></ul><ul><li>It is the Protein’s Primary Structure </li></ul>
  11. 12. Protein Folding Patterns <ul><li>Determines the specific function of the protein </li></ul><ul><li>- Non-functional proteins are proteins that have lost their folding patterns </li></ul><ul><li>Conformational Levels </li></ul><ul><li>Secondary </li></ul><ul><li>Tertiary </li></ul><ul><li>Quaternary </li></ul>
  12. 13. Secondary Structure <ul><li>Interactions : Hydrogen bonding between backbone (carboxyl group and N-H) </li></ul><ul><li>Type of structures formed : </li></ul><ul><li>Alpha helix </li></ul><ul><li>Beta pleated sheet </li></ul>
  13. 14. Alpha Helix <ul><li>Carboxyl group and N-H are hydrogen bonded inside the helix. </li></ul><ul><li>Hydrophobic </li></ul><ul><li>R-groups are on the exterior of the helix </li></ul>
  14. 15. Beta pleated sheet <ul><li>Hydrogen bonding between Carboxyl and N-H groups that are far away on the polypeptide chain </li></ul>
  15. 16. Alpha & Beta: Working Together The green fluorescent protein : Composed of Beta pleated sheets (in yellow) which forms the outside structure of the protein and an alpha helix structure in the interior of the protein (in purple ).
  16. 17. Tertiary Structure <ul><li>Interactions: between distant R side groups in the polypeptide chain and with water. </li></ul>
  17. 18. <ul><li>Disulfide bonds : between cysteine R groups </li></ul><ul><li>Hydrogen bonding : (a.) between R-groups containing alcohol and acid, (b.) between an alcohol and an amide or amine, </li></ul><ul><li>1. alcohols: serine, Threonine , Tyrosine . </li></ul><ul><li>2. acids: aspartic acid, glutamic acid </li></ul><ul><li>3. amine: lysine </li></ul><ul><li>4. amide: asparagine </li></ul><ul><li>Hydrophobic Interactions: </li></ul><ul><li>“ Van der Waals forces” </li></ul><ul><li>Between non polar groups:  Valine, Proline </li></ul>
  18. 20. Quaternary Structure <ul><li>Not all proteins have a quaternary structure </li></ul><ul><li>Interactions : between different polypeptide chains (hydrogen bonding, hydrophobic interactions, Van der Walls) </li></ul>
  19. 21. Quaternary Protein: Antibody Light chain & Heavy Chain connected by di-sulfide bonds

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