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Proline Residues in Proteins

  1. Charles M Deber1,
  2. Barbara Brodsky2,
  3. Arianna Rath1

Published Online: 19 APR 2010

DOI: 10.1002/9780470015902.a0003014.pub2



How to Cite

Deber, C. M., Brodsky, B. and Rath, A. 2010. Proline Residues in Proteins. eLS. .

Author Information

  1. 1

    University of Toronto, Hospital for Sick Children, Ontario, Canada

  2. 2

    Robert W. Johnson Medical School, Piscataway, New Jersey, USA

Publication History

  1. Published Online: 19 APR 2010


As the only commonly occurring imino acid in proteins, proline has been found to play unique structural and dynamic roles in guiding protein folding, fibre formation and protein–protein interactions. The cyclic pyrrolidine side-chain fixes the backbone dihedral ϕ angle and renders proline unable to act as a hydrogen bond donor. These properties are reflected in its preference for protein secondary structure elements such as turns and polyproline II helices, and its generally destabilizing effect on α helix and β-strand conformation. The ability of proline to undergo cis-trans isomerization is important in protein folding and forms the basis of molecular switches that help to control cellular growth and regulation. Proline and its posttranslationally modified analogue, hydroxyproline, are additionally the major components of collagens, proteins that are the major fibrous proteins in animals and account for approximately 30% of total human body protein.

Key Concepts:

  • The structural and dynamic properties imparted to proteins by the amino acid proline arise from the unique cyclic structure of its side-chain.

  • Interconversion of proline from cis to trans conformation, which can be facilitated by peptidylprolyl isomerases, is a rate-limiting step in protein folding and can act as a molecular switch in the regulation of cellular growth and signalling.

  • Proline residues facilitate the formation of protein secondary structure elements such as turns and the polyproline II helix, but typically disfavour α helix and β-strand conformations.

  • Proline and its posttranslationally modified analogue hydroxyproline are key components of the structural protein collagen.

  • Regions of water-soluble proteins rich in proline residues are often sites of protein–protein interaction.


  • proline;
  • hydroxyproline;
  • collagen;
  • polyproline II helix;
  • protein–protein interactions;
  • peptidylprolyl isomerase