Figure 1.
(A) Scheme of mutant LMB-2 [anti-Tac(Fv)-PE38] with one cysteine in the connector. The positions of amino acids that span PE sequences are numbered. The amino acid sequence of the connector (C) of mutant LMB-2 (cys1-LMB-2) is changed from ASGGPE to ASGCGPE. VH, heavy chain fragment of anti-Tac antibody; L, peptide linker (GGGGS)3; VL, light chain fragment; C, connector; II, PE domain II; Ib, PE domain Ib; III, PE domain III. (B) Site-specific PEGylation to a cysteine residue in the connector of mutant LMB-2. cys1-LMB-2 is site-specifically conjugated with PEG via the formation of a thioether bond between a free thiol group in the connector of mutant LMB-2 and maleimide at one end of the PEG chain.