FIG. 2.

Schematic representation of the membrane topology of the sensor kinase RegB. The bold numbers give the position of the last amino acid of RegB, which was fused to LacZ (first amino acid Ala) or to PhoA (first amino acid Ser). Two additional amino acids have been introduced by the cloning procedure. The units of activity for β-galactosidase and alkaline phosphatase in E. coli are given below the number for the fusion position. The activities measured in parental strains were subtracted, and average values from at least three measurements were calculated. E. coli cultures were grown semiaerobically in Luria-Bertani medium to late exponential phase. n.d., not determined.