Table 3.

Summary of two-component fit parameters for arrays containing engineered defects.

		f(x) = Ae−x/τ +c
Receptor	Label Density (%)	τ (A)	c
Tsr-WT	0	46 ± 9 (0.47 ± 0.06)	0.53 ± 0.06
Tsr-V398C/WT	0	40 ± 10 (0.46 ± 0.06)	0.54 ± 0.05
Tsr-V398C/WT	2.4 ± 0.3	47 ± 8 (0.91 ± 0.07)	0.09 ± 0.07
Tsr-V398C/WT	6.0 ± 0.2	23 ± 3 (0.92 ± 0.02)	0.08 ± 0.09
Tsr-V398C/WT	50 ± 2	5 ± 2 (0.96 ± 0.06)	0.04 ± 0.03

The indicated values are averages ± standard deviations. The receptor population in isolated bacterial membranes was labeled at a specific, engineered, non-perturbing Cys residue (V398C) with the indicated final density of 5-iodoacetamido-fluorescein. The resulting chemical modification prevents CheA and/or CheW binding to the labeled receptor. Finally, the effect of the indicated labeling density on the decay kinetics of CheA kinase activity (Eq. 4) was quantitated in a five-day timecourse, yielding the lifetime (τ) and amplitude (A) of the quasi-stable component, as well as the amplitude (c) of the ultra-stable component.