Fig 2. Organization of the expression cassette within the plasmid pTM 875.

Expression was driven by a T7 promoter as shown in (A). The Vpu gene is flanked by the PelB signal peptide at the N-terminus that directs the protein to the periplasmic space of the bacteria and facilitates integration into the inner membranes, and a 6x- histidine tag at the C- terminus to aid in purification. (B) shows the sequence of the PelB signal peptide (in orange), Vpu (in green) and histidine tag (in blue). Chymotrypsin cleavage sites are denoted by down-pointing arrows (⬇) for strong recognition sites and by an asterisk (*) for secondary sites.