Non-Steric Interactions Predict the Trend and Steric Interactions the Offset of Protein Stability in Cells

Chemphyschem. 2018 Sep 18;19(18):2290-2294. doi: 10.1002/cphc.201800534. Epub 2018 Jun 21.


Although biomolecules evolved to function in the cell, most biochemical assays are carried out in vitro. In-cell studies highlight how steric and non-steric interactions modulate protein folding and interactions. VlsE and PGK present two extremes of chemical behavior in the cell: the extracellular protein VlsE is destabilized in eukaryotic cells, whereas the cytoplasmic protein PGK is stabilized. VlsE and PGK are benchmarks in a systematic series of solvation environments to distinguish contributions from non-steric and steric interactions to protein stability, compactness, and folding rate by comparing cell lysate, a crowding agent, ionic buffer and lysate buffer with in-cell results. As anticipated, crowding stabilizes proteins, causes compaction, and can speed folding. Protein flexibility determines its sensitivity to steric interactions or crowding. Non-steric interactions alone predict in-cell stability trends, while crowding provides an offset towards greater stabilization. We suggest that a simple combination of lysis buffer and Ficoll is an effective new in vitro mimic of the intracellular environment on protein folding and stability.

Keywords: FRET; laser-induced temperature-jump; macromolecular crowding; protein folding; quinary interactions.

Publication types

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

MeSH terms

  • Antigens, Bacterial / chemistry
  • Antigens, Bacterial / metabolism*
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / metabolism*
  • Borrelia burgdorferi / metabolism
  • Ficoll / chemistry
  • Kinetics
  • Lipoproteins / chemistry
  • Lipoproteins / metabolism*
  • Osmolar Concentration
  • Phosphoglycerate Kinase / chemistry
  • Phosphoglycerate Kinase / metabolism*
  • Protein Folding
  • Protein Stability
  • Saccharomyces cerevisiae / enzymology
  • Saccharomyces cerevisiae / metabolism
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transition Temperature


  • Antigens, Bacterial
  • Bacterial Proteins
  • Lipoproteins
  • Saccharomyces cerevisiae Proteins
  • VlsE protein, Borrelia burgdorferi
  • Ficoll
  • Phosphoglycerate Kinase