Fig. 4.

Dose–response measurements made by BRET. (a) Time course of the Y/C ratio (normalized to its prestimulus value) during a typical dose–response experiment with cheR cheB cells (VS151) expressing CheZ–RLUC and YFP–CheY. Aliquots of α-methylaspartate were added at times indicated by the solid arrows. A single saturating dose was added to a second set of cells at the time indicated by the dashed arrow. (b) Dose–response measurements for strains expressing Tar in different modification states: from left to right, cheR cheB (VS148, half-modified: ■), cheR cheB tar[QEQQ] (VS150, 3/4 modified: •), and cheB (VS179, fully modified: ▴).