Stereoelectronic and steric effects in side chains preorganize a protein main chain

Proc Natl Acad Sci U S A. 2010 Jan 12;107(2):559-64. doi: 10.1073/pnas.0909592107. Epub 2009 Dec 31.


Preorganization is shown to endow a protein with extraordinary conformational stability. This preorganization is achieved by installing side-chain substituents that impose stereoelectronic and steric effects that restrict main-chain torsion angles. Replacing proline residues in (ProProGly)(7) collagen strands with 4-fluoroproline and 4-methylproline leads to the most stable known triple helices, having T ( m ) values that are increased by > 50 degrees C. Differential scanning calorimetry data indicate an entropic basis to the hyperstability, as expected from an origin in preorganization. Structural data at a resolution of 1.21 A reveal a prototypical triple helix with insignificant deviations to its main chain, even though 2/3 of the residues are nonnatural. Thus, preorganization of a main chain by subtle changes to side chains can confer extraordinary conformational stability upon a protein without perturbing its structure.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Collagen / chemistry*
  • Crystallography, X-Ray
  • Drug Stability
  • Electronics
  • Models, Molecular
  • Molecular Conformation
  • Proline / analogs & derivatives
  • Proline / chemistry
  • Protein Binding
  • Protein Conformation
  • Protein Folding
  • Proteins / chemistry*
  • Proteins / metabolism
  • Solubility
  • Stereoisomerism


  • 4-methylproline
  • Proteins
  • fluoro-proline
  • Collagen
  • Proline

Associated data

  • PDB/3IPN