Fig. 3.

The molecular interface between MS2 and the F-pilus. a Four F-pilin subunits, which have specific interactions with the Mat, are colored tan, orange, gold, and khaki, respectively. The inset shows the overall side view of the F-pilus/Mat complex and the location of these four F-pilins within the pilus. Three aspartic acids are labeled as sphere models and the N terminus of one pilin is labeled by a black sphere. Arrows indicate the viewing directions for panels b–d. b The negatively charged residue Asp7 (red bead) from one F-pilin is in close proximity to the positively charged His357 (blue bead) from the Mat. c The negatively charged residues Asp7 and Asp23 (red beads) from two F-pilins are in close proximity to Arg36 and Arg99 (blue beads) from the Mat, respectively. d The N terminus of one pilin extends into a hydrophobic pocket consisting of five hydrophobic residues (Val15, Phe31, Leu33, Phe92, and Phe94, labeled by gray beads) from the Mat. The dashed black line denotes the location of the five missing residues (AGSSG) at the N terminus of one pilin. The cryo-EM density map is shown as a gray transparent envelope