Protein structure


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Interesting presentation that lays out the different levels or protein structure. Some problems

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Protein structure

  1. 1. Structure of Protein Anas Bahnassi
  2. 2. Peptides and proteins are polymers of amino acids linked together by amide bonds
  3. 3. Formation of Peptide Bond
  4. 4. Peptide Bond
  5. 5. Primary Structure of ProteinsThe particular sequence of amino acids that is thebackbone of a peptide chain or protein Ala-Leu-Cys-Met CH3 CH3 S CH CH3 SH CH2 CH3 O + CH O CH2 O CH2 O -H3N CH C N CH C N CH C N CH C O H H H
  6. 6. Because amino acids have two functional groups, aproblem arises when one attempts to make a particularpeptide
  7. 7. Formation of Disulfide BondsDisulfides can be reduced to thiols
  8. 8. The disulfide bridge in proteins contributes to the overall shape of a protein
  9. 9. Strategy for Making a Specific Peptide Bond
  10. 10. Amino acids can be added to the growing C-terminal endby repeating these two steps
  11. 11. When the desired number of amino acids has beenadded to the chain, the protecting group can beremoved
  12. 12. An Improved Peptide Synthesis Strategy
  13. 13. The first step in determining the sequence of amino acidsin a peptide or protein is to cleave the disulfide bridges
  14. 14. The next step is to determine the number and kinds ofamino acids in the peptide or protein 6 N HCl protein amino acids 100°C 24 h
  15. 15. The N-terminal amino acid of a peptide or a protein canalso be determined by Edman degradation
  16. 16. The particular PTH-amino acid can be identified bychromatography using known standards
  17. 17. The C-terminal amino acid can be identified by treatingthe protein with carboxypeptidase
  18. 18. Cyanogen bromide causes the hydrolysis of the amidebond on the C-side of a methionine residue
  19. 19. Secondary Structure of Protein• Describe the conformation of segments of the backbone chain of a peptide or protein• Identified by the following factors: • Regional planarity about each peptide bond • Maximization of the number of peptide groups that engage in hydrogen bonding • Adequate separation between nearby R groups.
  20. 20. Secondary Structure – Alpha Helix• Three-dimensional arrangement of amino acids with the polypeptide chain in a corkscrew shape• Held by H bonds between the H of –N-H group and the –O of C=O of the fourth amino acid along the chain• Looks like a coiled “telephone cord”
  21. 21. The a-Helix Is Stabilized by Hydrogen BondsProlines are helix breakers
  22. 22. Secondary Structure – Triple Helix• Three polypeptide chains woven together• Glycine, proline, hydroxy proline and hydroxylysine• H bonding between –OH groups gives a strong structure• Typical of collagen, connective tissue, skin, tendons, and cartilage
  23. 23. Two Types of b-Pleated Sheets
  24. 24. Tertiary Structure• Specific overall shape of a protein• Cross links between R groups of amino acids in chain disulfide –S–S– ionic –COO– H 3 N +– H bonds C=O HO– hydrophobic –CH3 H3C–
  25. 25. Tertiary Structure• The tertiary structure is defined by the primary structure.• The stabilizing interactions include covalent bonds, hydrogen bonds, electrostatic attractions, and hydrophobic interactions.• Disulfide bonds are the only covalent bonds that can form when a protein folds.
  26. 26. Globular and Fibrous ProteinsGlobular proteins Fibrous proteins“spherical” shape long, thin fibers Insulin Hair Hemoglobin Wool Enzymes Skin Antibodies Nails
  27. 27. Most globular proteins have coilconformations
  28. 28. The tertiary structure is the three-dimensionalarrangement of all the atoms in the protein
  29. 29. Quaternary Structure• Proteins with two or more chains• Example is hemoglobin Carries oxygen in blood Four polypeptide chains Each chain has a heme group to bind oxygen
  30. 30. Test your knowledgeIndicate the type of structure as(1) primary (2) alpha helix(3) beta pleated sheet (4) triple helixA. Polypeptide chain held side by side by H bondsB. Sequence of amino acids in a polypeptide chainC. Corkscrew shape with H bonds between amino acidsD. Three peptide chains woven like a rope
  31. 31. Test your knowledgeSelect the type of tertiary interaction as (1) disulfide (2) ionic (3) H bonds (4) hydrophobicA. Leucine and valineB. Two cysteinesC. Aspartic acid and lysineD. Serine and threonine
  32. 32. Test your knowledgeIdentify the level of protein structure1. Primary 2. Secondary3. Tertiary 4. QuaternaryA. Beta pleated sheetB. Order of amino acids in a proteinC. A protein with two or more peptide chainsD. The shape of a globular proteinE. Disulfide bonds between R groups
  33. 33. PharmaceuticalBiotechnologyAnas Bahnassi PhD RPh attribution – non-commercial – share alike