CHMI 2227E Biochemistry I

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CHMI 2227EBiochemistry I

• Proteins
• Tertiary structure

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Tertiary structure
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Tertiary structure

• Secondary structure
• Involves a single type of structure
• a-helix
• b-pleated sheet
• Presence of interactions between amino acids that
  are close together in the primary structure
• Main type of interaction H bonds.
• Necessary but not sufficient to make a functional
  protein.

• Tertiary structure
• Involves the folding, in space, of the whole
  polypeptide chain
• Involves several elements of seconday structures,
  whichy interact together through different
  interaction forces/bonds
• H bonds
• Electrostatic interactions
• Van der Waals interactions
• Hydrophobic interactions
• Disulfide-bonds
• Absolutely required for a protein to be active.
• Two main types of tertiary structures exist
• Fibrous (e.g. collagen)
• Globular (e.g. myoglobin)

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Tertiary structureInteraction forces

• For proteins in an aqueous environment
• Hydrophobic amino acids are buried in the
  interior of the structure
• Hydrophilic amino acids are exposed to the
  solvent
• Conversely, membrane-bound proteins are exposed
  to an hydrophobic environment
• Hydrophobic amino acids are exposed
• Hydrophilic amino acids are buried inside.

Check this one out http//www.elmhurst.edu/chm/v
chembook/567tertprotein.html
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Tertiary structure

• Protein folding occurs in specific steps
• Some individual elements of secondary structure
  are first formed
• A few elements of secondary structure cluster
  together to form conserved folding motifs
• These bundles of secondary structure then form
  domains, which fold independently of the rest of
  the protein
• Finally, several domains interact to form the
  final, functional 3-D structure of the protein.
• Any given protein will always adopt the same
  functional 3-D structure.

A
B
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Tertiary structureFolding motifs - 1
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Tertiary structureFolding motifs - 2
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Tertiary structureProtein domains Pyruvate
kinase
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Tertiary structure1. Myoglobin

• Found in muscles
• Binds the oxygen required for aerobic metabolism
• Associated with a heme group, which is actually
  responsible for binding oxygen

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Tertiary structure1. Myoglobin
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Tertiary structure2. Porin a membrane-bound
protein
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Tertiary structureChaperones

• For some proteins, folding requires the help of
  other proteins called chaperones
• Chaperones generally work by binding to exposed
  hydrophobic patches on the unfolded protein,
  preventing aggregation and irreversible
  inactivation.

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Tertiary structureProtein denaturation

• Proteins can be denatured by treatments that
  destroy the interaction forces required for the
  adoption of the proper 3-D structure
• Heat
• pH
• Solvent
• Urea/guadinium breaks up H-bonds
• b-ME

Check this one out http//www.elmhurst.edu/chm/v
chembook/568denaturation.html
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Tertiary structureProtein denaturation

• The fact that ribonuclease can be reversibly
  denatured and renatured in vitro shows that the
  information required for the proper folding of a
  protein resides in its primary structure.

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Examples of proteins1. Green fluorescent protein

• Protein found in the jelly fish
• Has the unique property to emit a green light
• Different variants were produced by genetic
  engineering to produce red, yellow, cyan, blue
  light.
• Extremely useful in cell biology one can tag it
  to her/his protein of interest and follow the
  protein in the cell using fluorescence microscopy.

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Examples of proteins1. Green fluorescent protein
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Examples of proteins1. Green fluorescent protein
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Examples of proteins1. Green fluorescent protein
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Examples of proteins2. Prion proteins
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Examples of proteins2. Prion proteins
Fiber aggregation
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Important web sitehttp//www.pdb.org/pdb/home/ho
me.do