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Protein structure & function


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Published in: Health & Medicine

Protein structure & function

  1. 1. Protein Structure and Function
  2. 2. Shape = Amino Acid Sequence Proteins are made of 20 amino acids linked by peptide bonds Polypeptide backbone is the repeating sequence of the N-C-C-N-C-C… in the peptide bond The side chain or R group is not part of the backbone or the peptide bond
  3. 3. Polypeptide Backbone
  4. 4. Amino Acids NOTE: You need to know this table Hydrophilic Hydrophobic
  5. 5. Protein Folding The peptide bond allows for rotation around it and therefore the protein can fold and orient the R groups in favorable positions Weak non-covalent interactions will hold the protein in its functional shape – these are weak and will take many to hold the shape
  6. 6. Globular Proteins The side chains will help determine the conformation in an aqueous solution
  7. 7. Hydrogen Bonds in Proteins H-bonds form between 1) atoms involved in the peptide bond; 2) peptide bond atoms and R groups; 3) R groups
  8. 8. Protein Folding Proteins shape is determined by the sequence of the amino acids The final shape is called the conformation and has the lowest free energy possible Denaturation is the process of unfolding the protein Can be down with heat, pH or chemical compounds In the chemical compound, can remove and have the protein renature or refold
  9. 9. Protein Folding 2 regular folding patterns have been identified – formed between the bonds of the peptide backbone α-helix – protein turns like a spiral – fibrous proteins (hair, nails, horns) β-sheet – protein folds back on itself as in a ribbon –globular protein
  10. 10. β Sheets Core of many proteins is the β sheet Form rigid structures with the H-bond Can be of 2 types Anti-parallel – run in an opposite direction of its neighbor (A) Parallel – run in the same direction with longer looping sections between them (B)
  11. 11. α Helix Formed by a H-bond between every 4th peptide bond – C=O to N-H Usually in proteins that span a membrane The α helix can either coil to the right or the left Can also coil around each other – coiled-coil shape – a framework for structural proteins such as nails and skin
  12. 12. Levels of Organization PrimaryPrimary structure Amino acid sequence of the protein SecondarySecondary structure H bonds in the peptide chain backbone  α-helix and β-sheets TertiaryTertiary structure Non-covalent interactions between the R groups within the protein QuanternaryQuanternary structure Interaction between 2 polypeptide chains
  13. 13. Protein Structure
  14. 14. Domains A domaindomain is a basic structural unit of a protein structure – distinct from those that make up the conformations Part of protein that can fold into a stable structure independently Different domains can impart different functions to proteins Proteins can have one to many domains depending on protein size
  15. 15. Domains
  16. 16. Useful Proteins There are thousands and thousands of different combinations of amino acids that can make up proteins and that would increase if each one had multiple shapes Proteins usually have only one useful conformation because otherwise it would not be efficient use of the energy available to the system Natural selection has eliminated proteins that do not perform a specific function in the cell
  17. 17. Protein Families Have similarities in amino acid sequence and 3-D structure Have similar functions such as breakdown proteins but do it differently
  18. 18. Proteins – Multiple Peptides Non-covalent bonds can form interactions between individual polypeptide chains Binding site – where proteins interact with one another Subunit – each polypeptide chain of large protein Dimer – protein made of 2 subunits  Can be same subunit or different subunits
  19. 19. Single Subunit Proteins
  20. 20. Different Subunit Proteins Hemoglobin 2 α globin subunits 2 β globin subunits