Three-in-one chromatography-free purification, tag removal, and site-specific modification of recombinant fusion proteins using sortase A and elastin-like polypeptides.

Applied in tandem, elastin-like polypeptides (ELPs) and the sortase A (SrtA) transpeptidase from provide a general method for chromatography-free purification of tag-free recombinant proteins and optional, site-specific and homogeneous conjugation of the protein to a small molecule. This system provides an efficient, practical mechanism for generating bioactive proteins and protein-small-molecule combination therapeutics at high yields and purities.