Figure 2

Modular structure of the Ag43 passengers belonging to classes 1, 2, 3 and 4. (A) Based on the experimentally determined L-shaped structure of Ag43^{C3-UPI00000E4A66} (PDB: 4KH3), three subdomains could be defined SL (for stem of the letter L), EJ (for elbow joint), and BL (for bottom of the letter L)²⁵. Both SL and BL subdomains exhibit a right-handed parallel β-helix, the cross-sections of each rung along SL form triangular (T) β-solenoids of subtype 4 (T4) and of T5-type β-solenoids for BL (Supplementary Table S1). The EJ subdomain is flanked by β-hairpin motifs with three-rung parallel T5 β-solenoids. (B) Molecular modelling of the structures of Ag43 passengers from C1 to C4 using Phyre^54,55. The SL domain is shown in shades of blue, with electric blue corresponding to SL1 and cyan to SL2. The EJ domain is depicted in shades of orange, with bright orange corresponding to EJ1 and light orange to EJ2. The BL domain is represented in shades of red, with bright red corresponding to BL1 and magenta to BL2. PT: prototypical variant.