Protein%20Structure%20

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Protein Structure Function

• Presented By
• Shyla Neher
• February 4, 2004

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Hierarchical Structure of Proteins

• A proteins structure determines its 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
• a-helix
• ß-sheet
• turns

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• 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

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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

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Enzymes

• Enzymes function to catalyze reactions
• Lowers activation energy
• Increases rate by 106 - 1012
• Does not change equilibrium of reaction
• Catalysis occurs at the active site
• Enzymes show high specificity

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Catalytic Action of an Enzyme
V max Maximal enzyme velocity Km Enzyme
affinity for its substrate
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Regulation of Protein Function

• Allosteric Mechanisms
• Phosphorylation and Dephosphorylation
• Proteolytic Activation
• Compartmentation
• pH and Temperature
• Prosthetic Groups
• Cofactors

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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

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• THANK YOU!