Patent ID: 7834258

Claim:
A recombinant fusion protein comprising: (i) a binding domain that is an antibody that binds to a cell-surface antigen; (ii) a functional group domain for eliciting a desired effect on a target molecule, wherein tile functional group is an enzyme; and (iii) an extension peptide located between said binding domain and said functional group domain and containing one uncoupled cysteine residue capable of forming a disulfide bond for dimerization, wherein the extension peptide has a sequence represented by (S/A)KPSI(S/A)T(K/Q)AS(G 4 S) n GGPE, which is SEQ ID NO:13, wherein (n) is an integer ranging from 0 to 8, and wherein the amino acid at position 4, 15, 25 or 35 of SEQ ID NO:13 is substituted with said cysteine residue capable of forming a disulfide bond.