Figure 1.

Incorporation of cysteine at strategic sites of the transmembrane barrel PagP. Schematic representation of PagP from E. coli (red) was generated using PyMOL (40) from the crystal structure (PDB: 3GP6 (34)). The structure of PagP is tilted by ∼25° with respect to the membrane normal and consists of eight transmembrane β-strands and a periplasmic α-helix. Host sites at which cysteine was introduced are highlighted as spheres along with the residue number. A total of 27 lipid-facing sites, including nine midplane residues (green spheres; note that strand 3 has two lipid-facing midplane residues), two lipid-facing residues on the terminal strand (residues 155 and 159; green spheres), and 16 residues lining the water-lipid interface (blue spheres) were chosen from across the eight β-strands of PagP for mutation to cysteine. To retain visual clarity, not all the spheres are numbered. To see this figure in color, go online.