Proteins

2. Proteins

3. Levels of Structure • Primary—sequence • Secondary—local structures, same in many different proteins • Tertiary—actual 3-D structure, unique for each protein • Quaternary—interactions between more than one peptides

5. Primary Structure

6. The Peptide Bond • Planar • Carbonyl and amino point in opposite directions • Leads to "ends" on protein

7. Bonds/Interactions in protein structure

8. Disulfide Bonds

10. Secondary Structure • Repetitive patterns of local structure • -helix • -sheet

11. -Helix • Linus Pauling and Robert Corey, 1953 • Right handed spiral • 3.6 aa/turn • Every 4th aa on same side • H-bonds run length of helix • R-groups stick out from sides

12. -sheet • 2 peptide backbones • Very open configuration • "Pleated" • Parallel and antiparallel

14. Tertiary Structure • Thermodynamically most stable form • Held together by • Hydrophobic interactions • Electrostatic interactions • -S-S- bonds • Can include non-protein groups • Prosthetic groups or co-enzymes • Determined by x-ray crystalography

15. Types of Tertiary Structures • Fibrous proteins • Silk • Keratin • Collagen • Globular proteins

20. Quaternary Structure