Figure 8
Dissimilar conformations of the α1–α2 motif in the immunity proteins of engineered Im7-like family structures. (A) The α1–α2 motifs in the two in vitro evolved immunity proteins (Im9-ie1, Im9-ie2) adopted the same unique conformation. The α1–α2 motifs are colored as follows: Im7, green; Im9, magenta, Im9-ie1 and Im9-ie2, blue. Colicins and immunity proteins are colored pink and light blue, respectively. (B) The α1–α2 motifs of the designed immunity proteins (Im2-des3, a “specific” design for Col-des3; Im2-des7, a “multi-specific” variant that recognizes three different designed colicins) adopt different conformations than in Im2. The angle of view is rotated 70° about the X-axis relative to A. The α1–α2 motifs of Im2, Im2-des3, and Im2-des7 are colored magenta, red, and yellow, respectively. (C) Structure-based sequence alignment of wild-type and engineered immunity proteins. The α1–α2 motifs are colored as follows: Im7, green; Im9 and Im2, pink; Im2 of a non-cognate pair (Im2-nc), brown; Im9-ie1 and Im9-ie2; blue; Im-des3, red; Im-des7, yellow. Mutations that were introduced into the engineered immunity proteins are marked in bold. Immunity protein positions are numbered according to Im7 (Im7#), shown with the Im7 and the Im9 secondary structure elements above and below the alignment.
