Fig. 2.

Expression of recombinant target modules. a Schematic representation of bispecific target modules 5FE, 5FE2 and 5FE3 consisting of an N-terminal ErbB2-specific scFv antibody fragment, hinge, CH2 and CH3 domains of human IgG4, followed by one, two or three E5B9 peptide sequences per monomer separated by G₄S linkers. Amino (N) and carboxy termini (C) of the proteins are indicated. Disulfide bridges within the hinge region facilitate homodimerization. b In target modules F5E, F5E2 and F5E3 the ErbB2-specific antibody domain is placed C-terminal of the IgG4 Fc region, followed by the E5B9 peptide sequences. c, d Immunoblot analysis of purified target modules under reducing (R) or non-reducing (NR) conditions with HRP-conjugated antihuman IgG antibody. The positions of TM monomers and dimers are indicated