FIG. 2.

Mutational analysis of the yopE minimal secretion signal. Single transversion mutations (from purines to pyrimidines and vice versa) were engineered into the first seven codons of yopE and fused to npt. A transversion mutation at nucleotide position 4, 11, or 14 would have resulted in a stop codon, so an alternate mutation was introduced. Fusions to Npt were analyzed for type III secretion as described in the legend to Fig. 1.