Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Location of VceC gain-of-function (gof) substitutions. Shown is a schematic representation of a single protomer of a Vibrio cholerae outer membrane efflux protein, VceC, indicating the location of the gof amino acid substitutions (in black) at the proximal end, which enables it to function with the Escherichia coli AcrAB efflux pump. The protomer is aligned vertically. The β-barrel is at the top (distal end), and the α-helical domain is at the bottom (proximal end). The crystal structure of VceC was downloaded from the Protein Data Bank website (http://www.rcsb.org/pdb/), and the schematic figure was rendered using the RasMol program. (See related article on page 3757.)