Molecular crowding effects on protein stability in a bacterial proteome

Area of Science:

• Biochemistry
• Cell Biology
• Proteomics

Background:

• Molecular crowding, the spatial restriction by macromolecules, influences cellular processes like protein folding and interactions.
• The cellular environment is highly crowded, impacting molecular behavior differently than dilute experimental conditions.
• The relative contributions of entropic and enthalpic effects in molecular crowding remain debated.

Purpose of the Study:

• To investigate the impact of common molecular crowders on the stability of a bacterial proteome.
• To determine how different crowding agents affect individual protein stability within a complex proteome.
• To elucidate the mechanisms underlying protein stability changes in response to molecular crowding.

Main Methods:

• Utilized Thermal Proteome Profiling (TPP) to assess protein melting temperatures across a heat gradient.
• Tested the effects of six different molecular crowding agents (Ficoll, dextran, PEG) on the proteome of Cupriavidus necator.
• Analyzed protein stability changes and correlated them with protein properties like hydrophobicity and function.

Main Results:

• All tested crowders reduced the global mean melting temperature of the proteome.
• Specific proteins exhibited significantly increased or decreased stability depending on the crowder.
• Proteins showing enhanced stability were often hydrophobic, enzymatic, or involved in protein interactions.
• Individual proteins displayed varied sensitivities to multiple crowding agents.

Conclusions:

• Molecular crowding agents differentially affect protein stability within a proteome.
• The findings support a direct binding or preferential exclusion model for enhanced protein stability.
• These results challenge models solely based on viscosity or general excluded volume effects.