Quantitative protein stability measurement in vivo

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Protein folding equilibrium is crucial for function and regulation.
• In vitro stability measurements may not reflect in vivo conditions.
• The cellular environment can significantly alter protein thermodynamic stability.

Purpose of the Study:

• To quantitatively compare protein stability in vitro versus in the cytoplasm of Escherichia coli.
• To investigate the impact of hyperosmotic stress on intracellular protein stability.
• To establish a method for measuring protein stability within living cells.

Main Methods:

• Utilized amide hydrogen exchange detected by MALDI mass spectrometry (SUPREX) for in vivo protein stability measurements.
• Compared thermodynamic stability of monomeric lambda repressor in vitro and in E. coli cytoplasm.
• Applied SUPREX to E. coli under both normal and hyperosmotic conditions.

Main Results:

• Monomeric lambda repressor exhibits identical thermodynamic stability in vitro and in E. coli cytoplasm under normal conditions.
• Hyperosmotic stress leads to a significant enhancement of in vivo protein stability.
• The in vivo SUPREX method successfully quantified intracellular protein stability changes.

Conclusions:

• Intracellular protein stability can be accurately measured using the in vivo SUPREX technique.
• The cellular environment's impact on protein stability is condition-dependent, as shown by hyperosmotic stress.
• This method offers valuable insights into protein behavior and regulation within living cells.