Fig. 2.
Crystallographic interactions between neighboring MexA molecules are mediated by conserved residues down the exposed surfaces of the MexA hairpin. (a) An alignment of the hairpin regions of eight drug efflux adaptors, adapted from Johnson and Church (13). Residues lying in the a and d positions of the hairpin are highlighted in yellow. Small residues on the exposed surfaces in position c and f of the hairpin are light green, with dark green indicating large hydrogen-bonding residues at the ends of these exposed surfaces. PA, P. aeruginosa; HY, Helicobacter pylori; EC, E. coli. The residue numbers are for mature proteins, after removal of the periplasmic signal sequences. (b) Three views of a surface representation of the MexA monomer. Small conserved residues are again colored light green whereas the larger hydrogen-bonding residues at either end of the conserved region are dark green.