Elementary plant Biochemistry and Biotechnology (2+1)

Helix structure

 
• The α-helix is the most stable arrangement of polypeptides.The helix structure of proteins is stabilized by intramolecular hydrogen bonding.
  
• In this structure, hydrogen bonds are formed between the C=O group of one peptide bond and the N-H group of another after 3 amino acid units.
• The polypeptide chain constituted by L-amino acids form a right-handed helix, whereas the polypeptide chains made up of D-amino acids form a left-handed helix.
• In the α-helical conformation, all the side chains lie outside the helix whereas C, N, O and H of the peptide bond lie in the same plane.
• Certain amino acids tend to disrupt the α-helix.
  
• Among these are proline (the N atoms is part of the rigid ring and no rotation of the N-C bond can occur) and amino acid with charged or bulk R groups that either electrostatically or physically interferes with helix formation