1. Protein Structure & Function Presented By: Shyla Neher February 4, 2004

2. Hierarchical Structure of Proteins A proteins structure determines it’s function Primary –Linear sequence of amino acid residues Peptide Polypeptide Secondary –Results in the folding of localized parts of a polypeptide chain –Stabilized by H bonding α-helix β-sheet turns

3. Tertiary –Three dimensional arrangement of all amino acid residues –Results from hydrophobic interactions and hydrogen bonding –Structure undergoes fluctuation Quaternary –Proteins that consist of 2 or more polypeptides –The number and position of the polypeptide

4. Protein Folding & Modification Most proteins form into their Native confirmation Folding is promoted by chaperones –Molecular Chaperones –Chaperonins Nearly all proteins undergo chemical modification after synthesis on a ribosome –Acetylation –Phosphorylation –Methylation

5. Enzymes Enzymes function to catalyze reactions –Lowers activation energy –Increases rate by 10 6 - 10 12 –Does not change equilibrium of reaction –Catalysis occurs at the active site Enzymes show high specificity

6. Catalytic Action of an Enzyme V max = Maximal enzyme velocity Km = Enzyme affinity for its substrate

7. Regulation of Protein Function Allosteric Mechanisms Phosphorylation and Dephosphorylation Proteolytic Activation Compartmentation pH and Temperature Prosthetic Groups Cofactors

8. Protein Purification In order to study protein it must be purified Methods of Purification –Centrifugation –Electrophoresis –Liquid Chromatography –Enzyme & Antibody Assays –Mass Spectrometry –X-ray Crystallography

9. THANK YOU!