Toxin
Discussing overall structure and implication of MSA in toxin
Analysis
The toxin’s transmembrane domain consists of two adjacent hydrophobic α-helices (helices α6 and α7, indicated in orange) that form a helical hairpin structure and are surrounded by other helices (indicated in turquoise) (Fig. 1). The hairpin structure is inserted into the membrane in a transmembrane orientation when the toxin binds to the phospholipid bilayer. Whether helices α6 and α7 of BID insert themselves into the membrane in the same fashion as the hairpin structure of the toxins is currently unknown.
Although there are no regions of high conservation between 2BID and the toxin (Table 1), the properties these regions hold are very similar.
Fig. 1. 1XDT diphtheria toxin. Hydrophobic helices are labeled in orange. all other helices are blue, and loop regions are magenta.
Table 1. Toxin Comparison. Protein conservation between 2BID and 1XDT. Areas of high conservation are noted with an asterisk.