Figure 6.

The rivet model of the transmembrane aerolysin β-barrel. Our model of the aerolysin transmembrane β-barrel is shown as a ribbon diagram from the side (A). One of the β-hairpins is highlighted in dark gray and the side chains are shown as balls and sticks. The membrane is shown as a semitransparent gray box. The rivet model as seen from the top (B) with the channel lining residues space-filled. Acidic residues are shown in red, basic residues in blue, polar uncharged residues in yellow and hydrophobic residues in gray. In this rivet model, the tip of each loop folds back, with the hydrophobic residues pointing up toward the core of the bilayer and the flanking charged residues snorkeling down toward the polar head groups. (C) Ribbon diagram of a side view of the Staphylococcal transmembrane β-barrel (Song et al, 1996). One of the β-hairpins is highlighted in dark gray and the side chains are shown as balls and sticks. (D) Space-filled model of the Staphylococcal transmembrane β-barrel (the cap and rim domains were omitted) viewed from the top, that is, the side where the cap domain is located. (E) Ribbon diagram of the β-barrel of the bacterial outer membrane iron transporter FhuA (Ferguson et al, 1998; Locher et al, 1998) (PDB code: 1BY3). The plug domain was omitted for clarity. Side chains for hairpins 9 and 10 are shown as balls and sticks using the same color code as in panel A. The hairpins 9 and 10 of FhuA were extracted from the structure to better illustrate side-chain conformations (F). Similar types of loops were found in osmoporin (Dutzler et al, 1999) (1OSM) (G) and in maltoporin loop (Meyer et al, 1997) (2MPR) (H).