Site-directed mutagenesis of BacA invariant residues.

a The C55-PP phosphatase assay was performed as described in Materials and Methods in the presence of 1 mM CaCl2. Results are expressed as mean ± standard deviation of three individual experiments.b Relative activities of BacA mutant proteins as compared to the wild-type protein. It should be noted that enzyme assays performed in our work and by Chang et al. used different substrates: C55-PP and C15-PP, respectively. ND, not done.c Plasmids expressing the wild-type or mutated bacA genes were tested for their capability to complement (i.e. to restore growth at 42°C of) the thermosensitive conditional mutant BWTsbacA. +, complementation; -, no complementation. In the case of the E21A, S27A and R174 mutants, the same results were observed when the gene expression was further increased by addition of IPTG (0.05 or 0.5 mM).Site-directed mutagenesis of BacA invariant residues.