Disclosed is a composition of matter involving a recombinant fusion protein comprising a a pharmacologically active protein partner, and a small pharmacologically inactive protein domain partner of human origin, such as but not limited to, a 10th fibronectin III domain, a SH3 domain, a SH2 domain, a CH2 domain of IgG1, a PDZ domain, a thrombospondin repeat domain, an ubiquitin domain, a leucine-rich repeat domain, a villin headpiece HP35 domain, a villin headpiece HP76 domain, or a fragment or modification of any of these. Also disclosed are nucleic acids (e.g., DNA constructs) encoding the fusion protein, expression vectors and recombinant host cells for expression of the fusion protein, and pharmaceutical compositions containing the recombinant fusion protein and a pharmaceutically acceptable carrier, and method of producing a pharmacologically active recombinant fusion protein.
