Amino Acids and Protein Structures

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Amino Acids and Protein Structures

• Tolu Ashimolowo
• Montara Peavy

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Alpha Helix

• Right handed helical structure
• 5.4 Å wide
• Side chain R groups project outward from the
  helix
• Dihedral angles
• H-bond formed b/w every 4th amino acid ( N-H
  bonds to CO)
• Polarity- () Amino Terminus, (-) Carboxyl
  Terminus

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Beta Pleated Sheets

• Parallel Amino group and Carboxyl group have
  the same orientation
• Anti-parallel Different orientation
• R group side chains project away from the sheets
• Hydrogen Bonding

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Amino Acid Structure

• Amino acids are organic molecules
• Alpha carbon located in the middle
• Composition H atom, Carboxyl group, Amino group
  R group
• Most oxidized carbon is found on the top
• L stereoisomer are the most common the OH (amino
  group) is left of the alpha carbon
• D stereoisomer the OH (amino group) is right of
  the alpha carbon

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Amino Acids

• Groups
• Polar
• Non-polar
• Aromatic
• Cationic
• Anionic

• Peptide Bond Formation
• Dehydration reaction
• Reaction b/w
• carboxyl group of one amino acid and the adjacent
  amino group of another

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Protein Structures
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Protein Structures

• Primary Structure- sequence of linear amino acids
  held together by covalent bonds
• Secondary Structure- composed of alpha helices
  and ß pleaded sheets held together by hydrogen
  bonding throughout the polypeptide backbone

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Protein Structures

• Tertiary A three dimensional configuration of
  alpha helices and ß pleaded sheets spawning from
  interactions b/w side chains, bonding H-bonding,
  van der Waals, hydrophobic covalent bonding
  (disulfide bridges)
• Quaternary- gt2 polypeptides formed into a subunit
  held together by hydrogen bonding yielding a
  functional protein

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References

• Biology By Campbell and Reece, 6th Ed., Benjamin
  Cummings, 2002
• Principles of Biochemistry by Lehninger, Nelson,
  and Cox, 4th Ed., W. H. Freeman and Co., 2005