Polyacrylamide-streptavidin: a novel reagent for simplified construction of soluble multivalent macromolecular conjugates

We have developed a soluble macromolecular conjugation reagent, polyacrylamide-streptavidin (PASA), for the simplified preparation of multivalent protein-protein conjugates. Soluble linear polyacrylamide, with a molecular weight of approximately 10(6), has carboxyl groups generated by limited alkaline hydrolysis. It is then activated with carbodiimide, separated from excess carbodiimide, and conjugated to streptavidin. The resulting conjugate, which has approximately 20 streptavidin residues per molecule, can bind biotinylated proteins to produce homo- or heteroconjugates of known composition. We have used this technique to prepare soluble multivalent heteroligating antibody conjugates that can bind either of two antigenically distinct cell lines, as well as reagents that specifically label murine tumor cells with different MHC class I antigens. The method is potentially useful for making multivalent arrays of epitopes for measuring low affinity interactions such as that between the T cell receptor and MHC molecules, as well as for making immunotoxins, tumor labelling conjugates, and complex immunogens.