AtaGenix Laboratories
AtaGenix Laboratories
Release time: 2026-03-27 View volume: 17
Inclusion bodies are aggregates of misfolded recombinant protein that accumulate in E. coli. While often seen as a problem, inclusion bodies can actually be an advantage — if you know how to refold them properly. This guide covers when refolding is the right strategy and how to optimize the process.
When E. coli overexpresses a recombinant protein, the cellular folding machinery can become overwhelmed. Proteins that fold slowly, contain disulfide bonds, or have hydrophobic domains tend to aggregate into dense, insoluble particles called inclusion bodies. These accumulate in the cytoplasm and can represent 50–90% of total target protein produced — a high yield of inactive material.
Try Soluble Expression First When:
The protein is small (<30 kDa), has no or few disulfide bonds, and solubility tags (MBP, SUMO, GST) haven’t been tested yet. Also try lower induction temperature (16–20 °C), reduced IPTG, or Arctic Express strains before committing to refolding.
Commit to Refolding When:
Soluble expression strategies have failed, or you specifically need high yield of a protein with multiple disulfide bonds (e.g., cytokines, growth factors, enzyme domains). Inclusion bodies also offer advantages: high purity starting material (~80% target protein), protection from proteolysis, and easy isolation by centrifugation.
1. Isolation: Lyse cells, pellet inclusion bodies by centrifugation (high density makes them easy to isolate), wash with detergent to remove membrane contaminants.
2. Solubilization: Dissolve inclusion bodies in strong denaturant (6–8 M urea or 6 M guanidine-HCl) with reducing agent (DTT or β-mercaptoethanol) to fully unfold the protein.
3. Refolding: Gradually remove denaturant by dilution, dialysis, or on-column refolding. Add oxidized/reduced glutathione (GSSG/GSH) redox pair to facilitate disulfide bond formation. Optimize protein concentration (typically 0.01–0.1 mg/mL to minimize aggregation), pH, temperature, and additives (arginine, glycerol, PEG).
4. Polishing: Remove aggregates by SEC or IEX, then validate activity by functional assay (enzyme activity, binding ELISA, cell-based assay).
Protein concentration too high: The #1 cause of reaggregation. Keep dilution refolding at ≤0.1 mg/mL.
Wrong redox conditions: Disulfide-rich proteins need optimized GSSG:GSH ratios (typically 1:5 to 1:10).
Denaturant removed too fast: Rapid dilution can trap kinetic folding intermediates. Stepwise dialysis or slow dilution improves yields.
Missing cofactors or chaperones: Some proteins require metal ions (Zn²+, Ca²+) or small-molecule chaperones (arginine) for correct folding.
Struggling with inclusion bodies? AtaGenix’s E. coli platform offers both soluble expression optimization and inclusion body refolding services with >95% overall project success rate.
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