Structural analysis of BslA. (A and B) Topological representation of (A) BslA and (B) the structurally similar β2-microglobulin (34) constructed using TopDraw (44). Yellow and green β-strands represent conservation with the canonical Ig fold and the hydrophobic cap, respectively. Blue β-strands and the red α−helix represent secondary structure not part of the classical Ig fold. (C and D) Ribbon representation of the structure of (C) BslA and (D) β2-microglobulin using the same color scheme as in A and B. The surface-exposed leucine, isoleucine, and valines are represented as sticks with magenta carbon atoms. (E and F) The hydrophobic regions of (E) BslA and (F) HFBII (35). The hydrophobic region is shown in green, and surface-exposed leucine, isoleucine, and valines are annotated.