Fig. 1: Construction of PuuE tube.

a AF2 prediction of the heterodimeric peptide pair, M3L2 (yellow) and p66α (blue). b Crystal structure of PuuE (PDB ID: 3CL6). C-terminus positions are circled. Detailed structure, face, side, and back are shown for clarity. c Schematic diagram of the protein sequence (top) and the AF2-predicted structures of PuuE-M and PuuE-p (bottom). PuuE-M and PuuE-p are coloured yellow and blue to match the respective peptides and overall structure to clear the tube structure (d). Symmetry of protein is represented with lines and square markers. The peptide parts, M3L2 and p66α, are highlighted in darker colours. The flexibility of the connecting segments, M3L2 and p66α, as predicted by AF2, is demonstrated using a single peptide structure shown on the right. Further details are provided in Supplementary Fig. 1. d Predicted model of closed structure, e.g., tube structure with C₄ symmetry, consisting of PuuE-M and PuuE-p. The repeat unit was highlighted within a double-framed box. e nsTEM images of tubular assemblies constructed from PuuE-M and PuuE-p; 12.5 μM PuuE-M and 12.5 μM PuuE-p in NaCl (+) buffer was incubated at 40 °C for 24 h and imaged via nsTEM. Scale bars, 1 μm (white), 50 nm (black).