Figure 4. The pilE Guanine Quartet (G4).

A. Gene map showing the location of the pilE-associated G4 forming sequence and the sRNA promoter required for antigenic variation at the pilE locus. B. The sequence upstream of pilE that forms a G4. Mutation of the boxed guanine residues lead to loss of antigenic variation implicating the G4 in antigenic variation. C. The parallel G4 structure of the pilE G4 as solved by NMR analysis.