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Introduction to Proteins

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Serum antifreeze proteins. Blood coagulation. Antibodies. Membrane Transport Nutrients. Signal Transduction Cell Surface Receptors. Structural Support Collagen ... – PowerPoint PPT presentation

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Title: Introduction to Proteins


1
Introduction to Proteins
2
Proteins(Amino Acids)
Only 20 naturally-occurring amino acids Only
linear structures
3
Functions of Proteins I
  • Catalysts and Metabolic Regulation Enzymes
  • Protection
  • Serum antifreeze proteins
  • Blood coagulation
  • Antibodies
  • Membrane Transport Nutrients
  • Signal Transduction Cell Surface Receptors
  • Structural Support Collagen

4
Functions of Proteins II
  • Coordinated Motion Muscle Contraction
  • Genetic Regulation DNA Binding Proteins
  • Transport Hemoglobin
  • Generation and Transport of Nerve Impulses
  • Nutrient Storage
  • Seed proteins
  • Casein in milk

5
Function of proteins largely due to properties of
constituent amino acids
6
Structure of Proteins
  • Simple Proteins
  • Conjugated Proteins
  • Cofactors
  • Prosthetic Groups
  • Oligomeric Proteins (more than one polypeptide
    chain)

7
Conjugated Proteins
8
Oligomeric Proteins(more than one polypeptide
chain)
  • Subunits held together by covalent or
    non-covalent linkages
  • Identical subunits
  • Non-identical subunits
  • Covalent linkages are not peptide bonds

9
Classes of Shape
  • Globular Proteins
  • Spherical
  • Soluble
  • Dynamic Function e.g. catalysis (enzymes)
  • Fibrous Proteins
  • Rod-like
  • Insoluble
  • Structural

10
Levels of Structure
  • Primary Structure amino acid sequence
  • Secondary Structure backbone structure
    (backbone atoms)
  • Tertiary Structure three dimensional folding
    (side chain atoms)
  • Quaternary Structure structural relations
    between subunits of oligomeric proteins

11
Conformation of Proteins(overall three
dimensional structure of a protein)
  • Conformation is a property of amino acid sequence
  • Chaperones assist in the proper folding of
    proteins

12
Supramolecular Structures
13
The Theoretical Possibilities for Polypeptides
are Unlimited
  • Actual Polypeptides are Somewhat Limited in Size
    and Composition

14
Bovine Insulin
Figure 5-1
15
Composition of Some Proteins
Table 5-1
16
Protein Purification and Analysis
  • Purifying a Protein Requiresa Strategy

17
Physical Characteristics Distinguishing Proteins
Page 97
18
Fractionation by Salting Out
Figure 5-5
19
Isoelectric Points of Several Common Proteins
Table 5-2
20
Ion Exchange Chromatography
Figure 5-6
21
Gel Filtration Chromatography
Figure 5-7
22
Affinity Chromatography
Figure 5-8
23
SDS-PAGE
Figure 5-9
24
Molecular Mass and Electrophoretic Mobility
Figure 5-10
25
Two-Dimensional Gel Electrophoresis
Figure 5-11
26
Primary Structure Determination
27
Strategy
  • Purification of protein to homogeneity
  • Prepare protein for sequencing
  • Sequence polypeptide chains
  • Organize completed structure
  • Nucleic Acid Sequencing

28
Prepare Protein for Sequencing
  • End Group Analysis How many different subunits
  • Cleavage of disulfide bonds
  • Separation and purification of the polypeptide
    chains
  • Amino acid composition

29
Sequence Polypeptide Chains
  • Specific peptide cleavage reactions
  • Separation and purification of peptide fragments
  • Sequence determination

30
Organize Completed Structure
  • Ordering peptide fragments
  • Assignment of disulfide bond positions
  • Determine position of amides
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