Extended Data Fig. 2: Screening of GI₄ designs and in vitro assembly of GI₄-F7 from purified components.

Expression and screening by SDS-PAGE for GI₄ designs a, GI₄-F2, b, GI₄-F6 and c, GI₄-F7. Bands for chains A (green arrow), B (blue arrow), and C (red) arrow are indicated. The presence of all three bands in the Ni²⁺ Elute lanes of GI₄-F6 and GI₄-F7 indicates interactions between the A, B, and C chains. For gel source data, see Supplementary Fig. 4. d, HisTrap elution chromatogram of AB bicistronic expression. Blue, absorbance at 280 nm; red, gradient elution. Peak 1 (P1) is predominantly ABB, P2 is predominantly AAB, and P3 is predominantly the A chain, which assembles into 60-subunit I3-01-like nanocages. e, Superdex 200 Increase 10/300 chromatogram of P1 from the HisTrap elution. The first peak following the void volume (1) is predominantly I3-01-like nanocages and (2) is predominantly ABB heterotrimer. f, Superdex 200 Increase 10/300 chromatogram of P2 from the HisTrap elution. (1) is predominantly I3-01-like nanocages and (2) is predominantly AAB heterotrimer. g, Superdex 200 Increase 10/300 chromatogram of P3 from the HisTrap elution. (1) is predominantly I3-01-like nanocages and (2) is predominantly AAB heterotrimer. h, SEC purification of GI₄-F7 on a Sephacryl S-500 HR 10/300 GL column. Peak 1 contains the assembly while peak 2 is residual homotrimer component.