Suggested Questions for Chapter 13:

1
Suggested Questions for Chapter 13 3, 4, 5, 7,
9, 12, 13 ,14 ,15 ,23, 25
2
Proteins
What do proteins do?
3
Proteins Carry Out Diverse Functions
Yet, what do all proteins have in common?
4
Proteins Carry Out Diverse Functions
But they are all polymers of amino acids
5
Amino Acid
The side chain gives each amino acid its distinct
characteristic.
Monomer
6
Twenty Amino Acids
-
-



7
Peptide Bond Formation
Dimer
8
Amino Acid Sequence Primary Structure
Secondary structure
Folding Process
Tertiary structure
9
Proper Folding is Important for Proper Function
10
The Protein Folding Problem

• The linear polypeptide chain folds in a
  particular arrangement, giving a
  three-dimensional structure.
• Proteins unfolded in vitro fold back to their
  original ("native") state when solution
  conditions are returned to those in which the
  folded protein exists.
• All the information for the native fold appears
  therefore to be contained within the primary
  structure proteins are self-folding.

The problem lies in unlocking the relationship
between the sequence of amino acids and protein
structure.
11
AA Differences in b-chain of hemoglobin Among
Species
b-chain of hemoglobin is 146 AA long
Clearly, not all AA play a role in determining
3-D structure.
12
Insulin Folding
Denature
Wont renature
13
Posttranslational Processing
14
Posttranslational Processing
Making more than one protein from one gene
Another example of how the mammalian genome gets
the most out of its genes.
15
Amino Acid Sequence
What determines the amino acid sequence of a
protein?
16
Genes to Proteins
How do we know that genes determine proteins?
17
Genes to Proteins
Beadle and Tatum set out to provide experimental
proof of the connection between genes and
enzymes. They hypothesized that if there really
was a one-to-one relationship between genes and
specific enzymes, it should be possible to create
genetic mutants that are unable to carry out
specific enzymatic reactions.
To test this theory, they exposed spores of
Neurospora crassa (a bread mold) to X-rays or UV
radiation and studied the resulting mutations.
18
Proteins Are the End Products of Genes
Normally, the spores can be grown in minimal
medium.
19
Proteins Are the End Products of Genes
But after the x-irradiation, the spore would not
grow in minimal medium. However, they would
grow in medium enriched with vitamins, amino
acids, and nucleic acids.
20
Proteins Are the End Products of Genes
Beadle and Tatum Suggested that the mutant
lacked the enzyme to make trytophan. Thus, this
classic study linked mutations of a gene to loss
of metabolic enzyme activity.