Proteostasis Stress
Cellular stress arising when the protein quality control network is overwhelmed by misfolded or aggregated polypeptides.
Proteostasis Stress is the cellular condition in which the protein homeostasis (proteostasis) network—comprising chaperones, proteases, and the unfolded protein response—is overwhelmed by an excess of misfolded or aggregated polypeptides 1.
How It Works
Cells maintain proteostasis through a coordinated network of molecular chaperones (e.g., DnaK/DnaJ/GrpE, GroEL/GroES in E. coli) and degradation systems (Lon, ClpXP). When heterologous protein expression exceeds the capacity of these systems, unfolded intermediates accumulate and form toxic aggregates.
This stress activates heat-shock sigma factors and the unfolded protein response, diverting cellular resources toward damage control. Growth rate drops, plasmid-bearing cells lose competitive fitness, and product quality suffers as a fraction of target protein partitions into insoluble inclusion bodies.
Mitigation strategies include co-overexpression of chaperones, lowering induction temperature, using solubility-enhancing fusion tags, and tuning expression rate via weaker promoters or lower inducer concentrations.
Computational Considerations
Sequence-based solubility predictors such as CamSol and Aggrescan3D score aggregation propensity of candidate proteins. Kinetic models of the chaperone network estimate the folding load at given expression rates, helping engineers set induction levels that stay within the proteostasis capacity of the host 2.
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Proteome-wide aggregation propensity algorithms and chaperone network models predict which heterologous proteins will overload the folding machinery, guiding codon and expression-level tuning.