Hydrophobic surface burial is the major stability determinant of a flat, single-layer beta-sheet

J Mol Biol. 2007 Apr 20;368(1):230-43. doi: 10.1016/j.jmb.2007.02.003. Epub 2007 Feb 7.


Formation of a flat beta-sheet is a fundamental event in beta-sheet-mediated protein self-assembly. To investigate the contributions of various factors to the stability of flat beta-sheets, we performed extensive alanine-scanning mutagenesis experiments on the single-layer beta-sheet segment of Borrelia outer surface protein A (OspA). This beta-sheet segment consists of beta-strands with highly regular geometries that can serve as a building block for self-assembly. Our Ala-scanning approach is distinct from the conventional host-guest method, in that it introduces only conservative, truncation mutations that should minimize structural perturbation. Our results showed very weak correlation with experimental beta-sheet propensity scales, statistical beta-sheet propensity scales, or cross-strand pairwise correlations. In contrast, our data showed strong positive correlation with the change in buried non-polar surface area. Polar interactions including prominent Glu-Lys cross-strand pairs contribute marginally to the beta-sheet stability. These results were corroborated by results from additional non-Ala mutations. Taken together, these results demonstrate the dominant contribution of non-polar surface burial to flat beta-sheet stability even at solvent-exposed positions. The OspA single-layer beta-sheet achieves efficient hydrophobic surface burial without forming a hydrophobic core by a strategic placement of a variety of side-chains. These findings further suggest the importance of hydrophobic interactions within a beta-sheet layer in peptide self-assembly.

Publication types

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

MeSH terms

  • Alanine / genetics
  • Amino Acid Sequence
  • Amino Acid Substitution
  • Antigens, Surface / chemistry*
  • Antigens, Surface / genetics
  • Antigens, Surface / metabolism
  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / genetics
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Vaccines / chemistry*
  • Bacterial Vaccines / genetics
  • Bacterial Vaccines / metabolism
  • Borrelia burgdorferi
  • Crystallography, X-Ray
  • Glutamic Acid / genetics
  • Hydrophobic and Hydrophilic Interactions*
  • Lipoproteins / chemistry*
  • Lipoproteins / genetics
  • Lipoproteins / metabolism
  • Lysine / genetics
  • Models, Biological
  • Models, Molecular
  • Molecular Sequence Data
  • Mutant Proteins / chemistry
  • Protein Denaturation
  • Protein Folding*
  • Protein Structure, Secondary


  • Antigens, Surface
  • Bacterial Outer Membrane Proteins
  • Bacterial Vaccines
  • Lipoproteins
  • Mutant Proteins
  • OspA protein
  • Glutamic Acid
  • Lysine
  • Alanine

Associated data

  • PDB/2I5Z