FIG. 2.

Transmembrane topology of PhoR1 analyzed by lacZ protein fusions. (a) Domain structures of the chimeric proteins resulting from construction of three in-frame translational fusions between different sites of phoR1 and lacZ compared to that of PhoR1. (b) β-Galactosidase activities of E. coli strains harboring each translational fusion. The cells were grown on LB agar medium containing X-Gal. The numbers in parentheses indicate the β-galactosidase specific activity (pmol of o-nitrophenol produced per min and mg of protein) of each strain.