TABLE 2.

Degradation rates for endogenous SsrA-tagged proteins

Degradation of the endogenous pool of SsrA-tagged proteins was followed by blocking protein synthesis and measuring the remaining density following Western blotting as described under “Experimental Procedures.” The rates shown are the averages of the rates obtained in N independent experiments. Rates during exponential phase were obtained after fitting the graphs shown in supplemental Fig. S4 to a first-order exponential. Rates for stationary phase were derived from graphs of density data obtained from two independent experiments; representative blots are shown in Fig. 9, A—D. Standard deviations were determined as in Table 1.

Strain	Rate	Half-life	N
	min-1	min
Exponential phase
clpX	0.070 ± 0.01	9.9	4
clpX clpA	0.049 ± 0.01	14	4
clpX lon	0.037 ± 0.0004	19	2
clpX clpA lon	0.022 ± 0.0007	32	2
clpX clpS lon	0.043 ± 0.006	16	2
clpX sspBa	0.19 ± 0.004b	3.6	1
clpX clpA sspB	0.067 ± 0.02	10	2
clpX sspB lon	0.11 ± 0.02b	6.1	1
clpP	0.081 ± 0.020	8.6	4
clpP lon	0.0059 ± 0.0007	120	4
clpP clpQ	0.093 ± 0.01	7.5	4
clpP ftsHc	0.068 ± 0.005	10	2
Stationary phase
clpX	0.0068	100	2
clpX clpA	0.0142	50	2
clpX lon	0.0068	100	2
clpX clpA lon	0.0051	140	2

^aThis rate was obtained in one experiment. In other experiments (not shown) the rates were ∼0.07 min^-1 (see supplemental Fig. S4).

^bThis value represents the error in the slope calculated using a general curve fitting algorithm provided by the Kaleidagraph program (Pearson's r value >0.95).

^cThis strain grew poorly with a doubling time more than twice that of the other strains.