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. Author manuscript; available in PMC: 2017 Sep 25.
Published in final edited form as: J Mol Biol. 2016 Mar 24;428(19):3776–3788. doi: 10.1016/j.jmb.2016.03.017

Fig. 3. Stimulus response patterns of mutant receptors in an adaptation-deficient host.

Fig. 3

Mutant derivatives of plasmid pPA114 and pRR53 in strain UU2567 (CheR− CheB−) were tested for serine responses in FRET kinase assays. The YFP/CFP ratios reflect the level of receptor-controlled CheA kinase activity. Four different mutant receptor response patterns were seen in the UU2567 host:

upper left: Nonresponsive-ON receptors (ΔK215 shown) exhibited no activity changes in response to addition and removal of serine (SER; vertical gray bars), but activated CheA kinase, as evidenced by the response to KCN, which depletes cellular ATP, the phosphodonor for the CheA autophosphorylation reaction [34].

upper right: Nonresponsive-OFF receptors (ΔF208 shown) exhibited no serine or KCN responses and had low baseline values, indicating no receptor-stimulated kinase activity.

lower left: Responsive receptors (ΔS217 shown) exhibited kinase inhibition responses that saturated at high serine concentrations.

lower right: Partially responsive receptors (cc-6S shown; see Fig. 5) exhibited slow changes in kinase activity in response to both serine addition and removal (compare to the responsive example). Receptors of this type produced some kinase activity, but only inhibited a fraction of that activity at saturating stimulus levels.