FIG. 3.

Expression of clpC, clpP, and clpE is repressed by CtsR of S. pneumoniae. Expression of clpC′-bgaB (QB8071) (A), clpP′-bgaB (QB8069) (B), and clpE′-bgaB (QB8135) (C) in the presence (○, ●) or absence (□, ▪) of xylose. Cultures were grown in LB medium at 37°C to an OD₆₀₀ of 0.3, and xylose was added to one-half of the culture at a final concentration of 20 mM. Open symbols indicate the OD₆₀₀, and solid symbols indicate β-galactosidase specific activity, expressed as nanomoles of ONP per minute per milligram of protein.