Simultaneous phase transition of ELP tagged molecules and free ELP: an efficient and reversible capture system

In this paper, we demonstrate proof-of-principle for a method that allows selective recovery of molecules present at very low concentrations in complex mixtures. The method makes use of an elastin-like polypeptide (ELP) as a coaggregant for the capture of an ELP tagged recombinant protein present at concentrations as low as 10 pM, with a recovery higher than 90%. This coaggregation process was found to be independent of the concentration, at least up to 10 pM concentration of the ELP tagged protein. The coaggregation process is highly specific as was demonstrated by spiking crude cell lysate with the ELP tagged recombinant protein to a final concentration of 1 nM and recovering more than 80% of it to a high level of purity. The method should be particularly useful for high-throughput proteomic studies, where small amounts of poorly expressed proteins could be recovered for analysis by mass spectrometry. In a more general context, the concept presented in this paper provides a method that is highly efficient, specific, and fully reversible, which should render it useful in areas other than recombinant protein purification.