Fig. 8. Mutational analysis of the cotC promoter. (A) Deletion analysis. A 5' to 3' deletion series with a start point at nucleotide -659 (relative to the cap site) was constructed and fused to the lacZ gene at a point 30 nucleotides downstream from the cotC initiation codon. The constructs were used to prepare stable transformants in Ax2 and cudA-null cells and analysed as pooled populations. Note the shorter staining time used for the -659 construct. (B) Point mutation analysis. Site-directed mutagenesis was used to generate a construct with a 5' end point at nucleotide -457 and with a structure similar to that described in A. This construct, and the control wild-type construct, were analysed as in A but only in Ax2 cells.