Biosynthetic antibody binding sites

A single chain recombinant protein comprising a first polypeptide region peptide bonded to at least one other polypeptide region,

• one of said regions being immunologically reactive with a preselected antigenic site and comprising two polypeptide domains with the C-terminus of one peptide bonded to the N-terminus of the other through a polypeptide linker, each of said domains comprising a set of CDR amino acid sequences interposed between a set of FR amino acid sequences, said sets of CDR and FR sequences in said domains together defining a binding site immunologically reactive with said preselected antigenic site,
• another of said polypeptide regions being peptide bonded to the N- or C-terminus of said immunologically reactive binding site and comprising a single chain polypeptide having a conformation which confers biological activity to said another region under the same conditions that allow binding of said binding site region to said preselected antigenic site, said biological activity being independent of said binding site region.

A single chain recombinant binding protein comprising at least two regions,

• one of said regions comprising two polypeptide domains connected by a polypeptide linker, the amino acid sequence of each of said polypeptide domains comprising a set of CDRs interposed between a set of FRs, said sets of CDRs and FRs together forming a single chain binding site immunologically reactive with a preselected antigenic site,
• said polypeptide linker comprising plural, peptide bonded amino acids defining a polypeptide which spans the distance between the C-terminus end of one of said domains and the N-terminus and of the other of said domains when said binding site assumes a conformation suitable for binding, and comprising hydrophilic amino acids such that said linker assumes an unstructured polypeptide configuration in aqueous solution, and
• another of said regions comprising an amino acid sequence, peptide bonded to the N- or C- terminus of said binding site, comprising a single chain polypeptide having a conformation which confers biological activity to said another region under the same conditions that allow binding of said binding site to said preselected antigenic site, said biological activity being independent of said binding site region.

A single chain recombinant binding protein comprising at least two regions,

• one of said regions comprising at least two polypeptide domains connected by a polypeptide linker extending from the C-terminus of one to the N-terminus of the other, the amino acid sequence of each of said polypeptide domains comprising a set of CDRs interposed between a set of FRs, said sets of CDRs and FRs together comprising a single chain binding site immunologically reactive with a preselected antigenic site, said binding site having a binding affinity of at least 10.sup.6 liters/mole, and
• another of said regions comprising an amino acid sequence peptide bonded to the N- or C-terminus of said binding site, comprising a single chain polypeptide having a conformation which confers biological activity to said another region under the same conditions that allow binding of said binding site region to said preselected antigenic site, said biological activity being independent of said binding site region.