Fig. 1.

Locations of the mutations made in R16. (Top) Structural alignment of the sequences of R15, R16, and R17. The 106 residues in each domain are highlighted in bold. Each domain is extended by flanking residues. Helical regions indicated with h. The five core residues in Helix A described in this study are highlighted in red. (Bottom) R16 is shown as a cartoon with Glu18 shown in orange, Glu19 in purple, Ile22 in pink, Lys25 in dark green, and Val29 in pale green. Also shown is the conserved Trp21 in white.