Temperature dependence of protein folding kinetics in living cells

Minghao Guo, Yangfan Xu, Martin Gruebele

Research output: Contribution to journalArticlepeer-review


We measure the stability and folding rate of a mutant of the enzyme phosphoglycerate kinase (PGK) inside bone tissue cells as a function of temperature from38 to 48 °C. To facilitate measurement in individual living cells, we developed a rapid laser temperature stepping method capable of measuring complete thermal melts and kinetic traces in about two min.We find that this method yields improved thermal melts compared to heating a sample chamber or microscope stage. By comparing results for six cells with in vitro data, we show that the protein is stabilized by about 6 kJ/mole in the cytoplasm, but the temperature dependence of folding kinetics is similar to in vitro. The main difference is a slightly steeper temperature dependence of the folding rate in some cells that can be rationalized in terms of temperature-dependent crowding, local viscosity, or hydrophobicity. The observed rate coefficients can be fitted within measurement uncertainty by an effective two-state model, even though PGK folds by a multistate mechanism. We validate the effective two-state model with a three-state free energy landscape of PGK to illustrate that the effective fitting parameters can represent a more complex underlying free energy landscape.

Original languageEnglish (US)
Pages (from-to)17863-17867
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number44
StatePublished - Oct 30 2012


  • Activation barrier
  • Fluorescence microscopy
  • Förster resonance energy transfer (FRET)
  • Green fluorescent protein (GFP)
  • Thermal denaturation

ASJC Scopus subject areas

  • General


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