1. Historical Landmarks in Our Understanding of Proteins 1838The name "protein" (from the Greek proteios, "primary") was suggested by Berzelius for the complex organic nitrogen-rich substance found in the cells of all animals and plants. 1819-1904Most of the 20 common amino acids found in proteins were discovered. 1864Hoppe-Seyler crystallized, and named, the protein hemoglobin. 1894Fischer proposed a lock-and-key analogy for enzyme-substrate interactions. 1897Buchner and Buchner showed that cell-free extracts of yeast can ferment sucrose to form carbon dioxide and ethanol, thereby laying the foundations of enzymology. 1926Svedberg developed the first analytical ultracentrifuge and used it to estimate the correct molecular weight of hemoglobin. 1933Tiselius introduced electrophoresis for separating proteins in solution. 1942Martin and Synge developed chromatography, a technique now widely used to separate proteins. 1951Pauling and Corey proposed the structure of a helical conformation of a chain of L-amino acids -- the alpha helix -- and the structure of the beta sheet, both of which were later found in many proteins. 1955Sanger completed the analysis of the amino acid sequence of insulin, the first protein to have its amino acid sequence determined. 1956Ingram produced the first protein fingerprints, showing that the difference between sickle- cell hemoglobin and normal hemoglobin is due to a change in a single amino acid. 1963Monod, Jacob, and Changeux recognized that many enzymes are regulated through allosteric changes in their conformation.

2. Number & Size Distribution of Cellular Proteins

3. Size & Shape Comparisons of Proteins

4. Protein Structure and Function Protein Structure –Primary structure - amino acid sequence. –Secondary structure - formation of  helices and  sheets. –Tertiary structure - the three-dimensional conformation of a polypeptide chain. –Quaternary structure - formation of a protein molecule as a complex of more than one polypeptide chain.

5. Protein Structure and Function Protein Function –Enzymes - proteases, synthetases, polymerases, kinases –Structural - extracellularcollagen, elastin intracellulartubulin, actin,  -keratin –Transport - serum albumin, hemoglobin, transferrin –Motor - myosin, kinesin, dynein –Storage - ferritin, ovalbumin, calmodulin –Signaling - insulin, nerve growth factor, integrins –Receptor - acetylcholine receptor, insulin receptor, EGF receptor –Gene regulatory - lactose repressor, homeodomain proteins –Special purpose - green fluorescent protein, glue proteins

6. Protein Structure and Function Protein Structure –Primary structure - amino acid sequence. –Secondary structure - formation of  helices and  sheets. –Tertiary structure - the three-dimensional conformation of a polypeptide chain. –Quaternary structure - formation of a protein molecule as a complex of more than one polypeptide chain.

7. Amino Acids

8. Codon Usage Table

9. Protein Folding

10. Protein Denaturation & Refolding Protein confirmation is determined solely by its amino acid sequence

11. Protein Structure and Function Protein Structure –Primary structure - amino acid sequence. –Secondary structure - formation of  helices and  sheets. –Tertiary structure - the three-dimensional conformation of a polypeptide chain. –Quaternary structure - formation of a protein molecule as a complex of more than one polypeptide chain.

12.  helix Secondary Structure

13.  sheet Secondary Structure

14. Noncovalent Bonds

16. Hydrogen Bonds in Proteins

17. Noncovalent Bonds

21.  sheet Secondary Structure Antiparallel  sheet Parallel  sheet

22.  helix Interactions with Phospholipids

23. Protein Structure and Function Protein Structure –Primary structure - amino acid sequence. –Secondary structure - formation of  helices and  sheets. –Tertiary structure - the three-dimensional conformation of a polypeptide chain. –Quaternary structure - formation of a protein molecule as a complex of more than one polypeptide chain.

24. Tertiary Structure

25. Cytochrome b Lactate dehydrogenase IgG light chain

26. Structural Importance in Protein Function

27. Coiled-coiled Structure of Multiple  helices Asingle  helix with amino acids a and d being nonpolar. Btwo  helices wrap around each other with one nonpolar side chain interacting with the nonpolar side chain of the other. The hydrophilic side chains are exposed to the aqueous environment. Catomic structure of a coiled-coil showing the nonpolar interactions in red

28. Protein Structure and Function Protein Structure –Primary structure - amino acid sequence. –Secondary structure - formation of  helices and  sheets. –Tertiary structure - the three-dimensional conformation of a polypeptide chain. –Quaternary structure - formation of a protein molecule as a complex of more than one polypeptide chain.

29. Quaternary Structure

30. Hemoglobin

31. Protein - Protein Interactions A protein with just one binding site can form a dimer with an identical protein. Identical proteins with two different binding sites can form a long helical filament. If the two binding sites are located appropriately to each other, the protein subunits can form a closed ring instead of a helix.

32. Collagen and Elastin

33. Disulfide bonds