Characteristics of the PH1 bi- and tribody production systems. A, Schematic presentation of the assembled bibody and tribody molecules. Heavy chains are depicted in black, light chains in white, S-S: sulphur bond, E: E-tag (black square), H6: His-tag (black circle). B, Construction design for the heavy and light chain bi- and tribody expression cassettes. VH: variable heavy chain domain, CH1: constant heavy chain domain 1 (black). VL: variable light chain domain, CL: constant light chain domain (white). ss: signal sequence from BCL-1 (circle), L2: EPSGP(G4S)3 linker, L5: DVDGGSRGDGPG linker, L: (G4S)3 linker, E: E-tag (GAPVPYPDPLEPR) and H6: His6-tag. C, Schematic presentation of the pES31 mammalian expression plasmid carrying the strong βactin-βglobulin promotor. D, Schematic presentation of the pKai61 P. pastoris expression plasmid. Of note are the methanol induced AOX promoter and the S-tag (S) which is added to the gene insert. Also indicated (dotted line) is the place for gene insertion in the respective expression plasmids (C, D).