Saturated Alanine Scanning Mutagenesis of the Pneumococcus Competence Stimulating Peptide Identifies Analogs That Inhibit Genetic Transformation
Figure 4
The negative charge and enantiomericity of glutamate residue in the first position is important for the activity of CSP1.
(A) Amino acid substitutions of the first glutamate residue in CSP1. (B) Induction of comX expression by CSP1 analogs. D39pcomX::lacZ were incubated with CSP1 or with each glutamate substituted analog at a final concentration of 100 ng/ml. The ability of each peptide to induce the competence regulon was measured by induction of the comX by ß-galactosidase assays. (C) Genetic transformation of D39 cells in the presence of indicated concentrations of CSP1 and its analogs using the rpsL gene. Transformants were selected on THB agar containing 100 µg/ml streptomycin. Experiments in B and C were performed in triplicates and repeated three times. The means ± SD of one typical experiment are shown.