Chapter 5 Structure and Function of Protein

1. Chapter 5 Structure and Function of Protein

2. 1. Amino acids 5.1 Protein Components structure R--Different side chains, determin the properties of 20 amino acids. R NH3+ C COO- Carboxylic acid group Amino group H

3. Classification Hydrophobic-water fearing. non-polar side chains • Aliphatic • Aromatic • Sulfur containing • Polar/uncharged • basic/acidic Hydrophilic-water loving. polar, neutral chains negatively charged, positively charged

4. 2. Peptide bond Peptide Plane  Dihedral angle 3. Peptide and Polypeptide polypeptide protein oligopeptide dipeptide tripeptide decapeptide

5. 5.2 Protein Structure 1. Primary structure ----linear sequence of amino acids in a polypeptide chain 2. Secondary structure -helix -strand, -sheet, -barrel, -turn

6. 3. Tertiary Structure

7. 4. Quaternary Structure Hemoglobin - an example of a four-subunit protein Animation

8. 5. Bonds and Forces for Protein Structure ◆ Covalent bond ◆ Electrostatic interactions ◆ van der Waals interactions ◆ Hydrogen bonds ◆ Hydrophobic interactions

9. denaturation renaturation active inactive active 6. Denaturation and Renaturation of Protein

10. 5.3 Protein Folding 1. Concept Animation

11. Forces Involved in the Protein Folding ◆ Electrostatic interactions ◆ van der Waals interactions ◆ Hydrogen bonds ◆ Hydrophobic interactions

12. 3. Models for Protein Folding ◆ Framework Model ◆ Hydrophobic Collapse Model ◆ Nuclear-Condensation Model ◆ Diffusion-Collision model ◆ Funnel or Energy-landsape models

14. 5. Protein Misfolding and Diseases

15. 5.4 Structure and Function of Enzyme J.H.Northrop J.B.Sumner Most enzymes are proteins

16. 1. Proteins play key roles in a living system 2. Classification of enzymes Based on type of reaction Oxidoreductasecatalyze a redox reaction Transferasetransfer a functional group Hydrolasecause hydrolysis reactions Lyasebreak C-O,C-C or C-N bonds Isomerase rearrange functional groups Ligasejoin two molecules

17. 3. Structure of Enzyme (1) Active site  Catalytic site  Binding site (2) Specificity  Group specificity  Absolute specificity  Stereo specificity  Sequence specificity

18. 4. Catalysis Mechanism (1) Hypothesis/Theory  Lock and key model  Induced-fit model

19. HermannEmil Fischer The Nobel Prize in Chemistry 1902 Lock and key Theory (锁钥学说)

20. Daniel Koshland Professor, Biochemistry and Molecular Biology, University of California, Berkeley Induced –fit hypotheory (诱导契合假说) 1958 (1998 Albert Lasker Award )

21. Induced-Fit Model of enzyme catalysis

22. (2) Steps in an enzymatic reaction (3) Features of catalytic reaction ▼high efficiency ▼specificity ▼be regulated ▼inactive easily (4) Factors affecting enzyme activity Temperature  pH  Substrate concentration  Enzyme concentration

23. Summary 1. Peptide, polypeptide 2. Hierarchical protein structure. 3. Motifs and Domains of protein 4. Protein folding, misfolding and diseases 5. Protein functions and classification 6. Structure of enzyme and its specificity

24. Thank You Very Much