Rapid Establishment of Myeloma Cell Lines Expressing Fab(Tac)-Protamine, a Targetable Protein Vector, Directed Against High-Affinity -Chain of Human I
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A recombinant bifunctional fusion protein, consisting of a recombinant antibody and a DNA-binding protein, can be used as a nonviral gene delivery vector (Fig. 1 ). In this lab, such a fusion protein, composed of a human antibody Fab(105) moiety against the envelope glycoprotein of HIV-1, gp120, and a human DNA-binding moiety (protamine), was developed (1 ). Chen et al. (1 ) showed that the bifunctional fusion protein complexed with plasmid DNA, encoding the catalytic subunit of Pseudomonas exotoxin, a complex known as a genetic immunotoxin, and was specifically transferred into HIV-1-infected cells by receptor-mediated endocytosis, resulting in selective killing of the target cells. However, the low level of Fab(105)-protamine fusion protein secreted from the stably transduced COS cells has been a limiting factor for experiments requiring large amounts of the fusion protein.
Fig. 1. Schematic diagram of Fab(Tac)-protamine fusion protein. Recombinant Fab(Tac) antibody is composed of Fd fragment (VH and CH1 ), and κchain (VL and CL ) which are connected by a disulfide bond. Protamine protein is fused with the carboxyl end of Fd.
