Figure 1

Structural models and sequence alignment of Bri2 and Bri3 BRICHOS domains. Modelled structures of Bri2 (orange) and Bri3 (light blue) BRICHOS domains are shown from face A (a–c) or face B (d–f), and panels a and d show overlays of the two domains. The disulfide bond between the two strictly conserved cysteine residues (distance between the sulfur atoms of the two Cys is 2 Å) is highlighted in gold for Bri3 BRICHOS Residue side-chains that are highlighted by space-filling show either conserved (b and e) or changed (c and f, the residues shown are those present in Bri3 BRICHOS) charged residues between Bri2 and Bri3 BRICHOS, dark blue: positive charge, red: negative charge, grey: loss of charge to a neutral side-chain. (g) Sequence alignment of Bri2 and Bri3 BRICHOS. Shading represents identical residues (green) and similar residues (yellow), based on a Blosum62 score matrix with a threshold of 1. Residues indicated by small boxes above the sequences highlight the changed residues in panels c and f using the same colour-coding. A filled star highlights positions with conserved charge (also shown in b and e) and an open star indicates positions with varied charge (also shown in c and f) in the central β-sheet. The two conserved Cys are marked with yellow triangles.