Figure 6: Structure and aggregation propensity of protective antigen (PA) of B. anthracis.

(a) Monomeric PA is composed of four structural domains consisting predominantly of anti-parallel β-sheet: D1 is the calcium-binding domain (grey), D2 is the membrane insertion and heptamerization domain (red), D3 is the heptamerization domain (yellow) and D4 is the receptor binding domain (purple). (b) The intrinsic aggregation profile as predicted by TANGO indicated the presence of three main APRs, which are located in domains 3 and 4. The aggregation kinetics were shown to be dominated by the solvent exposed APR1 in the loop region of domain 3 (ref. 33). (c) MASS plots for the three APRs indicated in b. The mutations in APR 1 that we focused on are indicated in red.