Host-guest scale of left-handed polyproline II helix formation

Adam L. Rucker, Cara T. Pager, Margaret N. Campbell, Joseph E. Qualls, Trevor P. Creamer

Research output: Contribution to journalArticlepeer-review

127 Scopus citations


Despite the clear importance of the left-handed polyproline II (PPII) helical conformation in many physiologically important processes as well as its potential significance in protein unfolded states, little is known about the physical determinants of this conformation. We present here a scale of relative PPII helix-forming propensities measured for all residues, except tyrosine and tryptophan, in a proline-based host peptide system. Proline has the highest measured propensity in this system, a result of strong steric interactions that occur between adjacent prolyl rings. The other measured propensities are consistent with backbone solvation being an important component in PPII helix formation. Side chain to backbone hydrogen bonding may also play a role in stabilizing this conformation. The PPII helix-forming propensity scale will prove useful in future studies of the conformational properties of proline-rich sequences as well as provide insights into the prevalence of PPII helices in protein unfolded states.

Original languageEnglish
Pages (from-to)68-75
Number of pages8
JournalProteins: Structure, Function and Genetics
Issue number1
StatePublished - Oct 1 2003


  • Proline-rich sequences
  • Protein-protein interactions
  • Unfolded proteins

ASJC Scopus subject areas

  • Structural Biology
  • Biochemistry
  • Molecular Biology


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