Two possible quaternary arrangements of protein complexes containing two SBP(A18C) tags per SAVSBPM32 tetramer.

<p>(A) and (B) show the orientation of the two bound SBP tags (grey and orange) in a streptavidin tetramer. The N-terminal ends of the SBP tags are shown in cyan. Binding of these tags in Arrangement 1 results in a <i>trans</i>-oriented complex (E). (C) and (D) show how SBP-tags bind to the streptavidin tetramer in Arrangement 2, resulting in a <i>cis</i>-oriented complex (F). Streptavidin is colored yellow, red, blue and green for subunits A, B, C and D, respectively. Models were generated using PyMOL with PDB entry 4JO6 as the starting file.