Recombinant alpha-fetoprotein receptor-binding domain co-expression with polyglutamate tags facilitates in vivo folding in E. coli.

A wide range of methods are known to increase the prokaryotic intracellular recombinant proteins solubility, for instance, growth at low temperature, supplementation of culture media with "chemical chaperones" (proline, glycine-betaine, and trehalose), co-expression with chaperones or highly soluble fusion partners. As an alternative, we have introduced the polyglutamate tag, which, as it has been shown, increased the protein solubility and facilitated folding. In this study we evaluated the minimal quantity of high density negatively charged EEEEVE amino acid repeats (pGlu) necessary to switch the recombinant receptor-binding domain of human alpha-fetoprotein (rbdAFP) expression almost entirely from the inclusion bodies to the soluble cytoplasmic fraction in E.