Fig. 2.

Generation of the 1,3 trans-divalent streptavidin. (a) Amino acid sequence of streptavidin-E₆ (SAe) with E₆ tag red and underlined, along with Dead (D) streptavidin showing residues impairing biotin binding in blue. (b) Generation of the different valency forms of SAe/D by mixed refold and ion exchange, with predicted pI of monomer and tetramer indicated. (c) Ion-exchange chromatogram of a mixture of tetramers containing different proportions of SAe and D. (d) Analysis of peaks from ion exchange by SDS-PAGE with Coomassie staining, unboiled (left) to show tetramer mobility, or boiled (right) to show subunit composition.