Biomedical Fast Takes

Osmolytes for Proper Protein Folding

Since protein function depends on folding, the successful development of active pharmaceutical proteins are required for the in vitro production of functional, properly folded proteins. In vitro protein folding (and hence production) can be assisted by co-solvents, including osmolytes (these include betaine, inositol, taurine, glycerophosphocholine, choline, creatine, proline, alanine, and glycine) and arginine. Osmolytes accumulate in the liquid between the organelles in the cell interior. There, they raise the osmotic pressure against environmental water stresses, resulting in stabilization of proteins. They have been shown to enhance in vitro and in vivo protein folding and suppress in vivo protein aggregation. Thus they are called “chemical chaperones.”

Protein aggregates can be rescued
and their refolding assisted by an
dependent system.

The requirement of high concentrations, however, eliminates the possible applications of chemical chaperones to rescue in vivo misfolded proteins that cause various diseases. More specific ligands (ions or molecules that binds to a central metal atom to form a coordination complex) can serve a similar function at much lower concentrations and are called “pharmacological chaperones.”

In a new review, conducted at Alliance Protein Laboratories, in Thousand Oaks, California, the applications of chemical chaperones for biotechnology product development and of pharmacological chaperones for in vivo protein folding, and the mechanism of their effects on protein folding were investigated.1 A specific case reviewed was the mechanism of action of the polar amino acid arginine, which has been widely used in vitro as a chemical chaperone to assist protein folding and suppress aggregation.

In work done at the Biochemistry Unit, IFOM-IEO Campus for Oncogenomics, Cogentech in Milano, Italy, molecular chaperones and chemical compounds like amino acids and osmolytes were found to share the capability to prevent protein aggregation and contribute to rescue in vivo aggregated proteins. Therefore, both overexpression of the molecular folding machinery and induced accumulation of chemical chaperones are options to improve the correct folding of recombinantly expressed proteins.

These two parameters may show synergistic effects, although success remains protein specific and, therefore, several combinations of molecular and chemical chaperones should be compared in future research. However, proteins can fail to fold correctly even in optimized culture conditions. In this case, protein aggregates can be rescued and their refolding assisted by an osmolyte/chaperone-dependent system. The selection of aggregates with different degrees of complexity can be exploited to maximize the yields of native proteins at the end of the refolding process.


  1. Rajan RS, Tsumoto K, Tokunaga M, Tokunaga H, Kita Y, Arakawa T. chemical and pharmacological chaperones: application for recombinant protein production and protein folding diseases. Curr Med Chem 2011;18(1):1-15.
  2. de Marco A.Molecular and chemical chaperones for improving the yields of soluble recombinant proteins. Methods Mol Biol 2011;705:31-51.

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