. Author manuscript; available in PMC: 2013 Aug 1.

Published in final edited form as: Nat Chem Biol. 2012 Dec 2;9(2):90–96. doi: 10.1038/nchembio.1135

Table 1.

Cleavage activities of DegS trimers containing different numbers of PDZ domains and/or mutations in specific subunits

	Michaelis-Menten parameters
trimer	activating peptide	V_max/[E_total] (s⁻¹ trimer⁻¹)	K_M (μM)	substrate Hill constant
SSS	Tyr-Tyr-Phe	2.7 ± 0.1	300 ± 90	1.7 ± 0.1
^(a) DegS	Tyr-Tyr-Phe	2.6 ± 0.2	370 ± 40	1.4 ± 0.2
SSΔ	Tyr-Tyr-Phe	3.7 ± 0.5	360 ± 70	1.9 ± 0.3
SΔΔ	Tyr-Tyr-Phe	2.6 ± 0.2	490 ± 100	1.8 ± 0.4
ΔΔΔ	none	1.0 ± 0.3	400 ± 110	1.5 ± 0.1
^(b) DegS^ΔPDZ	none	0.8 ± 0.1	570 ± 50	1.7 ± 0.1
	Tyr-Tyr-Phe stimulated cleavage of 200 μM RseA^P
	basal activity (M⁻¹ s⁻¹)	maximal activity (M⁻¹ s⁻¹)	K_act (μM)	OMP peptide Hill constant
S^HP/SAΔΔ	590 ± 130	1700 ± 130	5 ± 2	1 ^(c)
S^SAΔΔ	110 ± 17	790 ± 50	18 ± 4	1 ^(c)
S^HP/SAS^HP/SAΔ	420 ± 140	1600 ± 410	7 ± 2	1.3 ± 0.3
S^SAS^SAΔ	4.5 ± 2	350 ± 32	38 ± 2	1.3 ± 0.1
SSΔ^YA	27 ± 4	400 ± 80	13 ± 1	1.4 ± 0.4
SSΔ	87 ± 7	3300 ± 480	14 ± 2	1.3 ± 0.1
SΔ^YAΔ^YA	17 ± 1	220 ± 39	25 ± 7	1 ^(c)
SΔΔ	360 ± 20	2900 ± 380	18 ± 6	1 ^(c)
SSΔ^SA	30 ± 9	2200 ± 300	19 ± 9	1.4 ± 0.3
SΔ^SAΔ^SA	95 ± 27	1300 ± 430	15 ± 5	1 ^(b)
SSS	< 5	3180 ± 80	16	1.7
^(a) DegS	2.9 ± 0.5	2500 ± 550	29 ± 3	1.7 ± 0.1
ΔΔΔ	575 ± 60	575 ± 60	n.a.	n.a.
^(b) DegS^ΔPDZ	590 ± 60	590 ± 60	n.a.	n.a.

^(a)

Data taken from ref. 26.

^(b)

Data taken from ref. 23.

^(c)

Data were fitted to a hyperbolic binding isotherm. Errors were calculated as $\sqrt{\frac{1}{(n - 1)} \sum_{1}^{n} {(value - mean)}^{2}}$ , where n is the number of independent trials (typically 2 or 3). Maximal activities for enzymes containing PDZ domains were determined in the presence of 150 μM Tyr-Tyr-Phe tripeptide; basal activity was determined in the absence of OMP peptide. K_act is the concentration of Tyr-Tyr-Phe tripeptide required for half-maximal stimulation of RseA^P cleavage. (n.a.) not applicable.