. Author manuscript; available in PMC: 2009 May 1.

Published in final edited form as: Nat Struct Mol Biol. 2008 Oct 19;15(11):1147–1151. doi: 10.1038/nsmb.1503

Table 1.

Protein-degradation and ATPase activities of Ar-Φ loop mutants of ClpX RWE/RWE.

		titin^CM-ssrA				titin-ssrA
ClpX variant	basal ATPase (min⁻¹)^a	K_M (µM)^b	Vmax (min⁻¹)^b	Working ATPase (min⁻¹)^c	ATP per substrate^d	K_M (µM)^b	V_max (min⁻¹)^b	Working ATPase (min⁻¹)^c	ATP per substrate^d
RWE	380	1.5	1.4	140	100	2.1	0.075	110	1,500

R^Y153AWE	860	19	3.1	370	120	18	0.017	250	15,000
RW^Y153AE	760	60	0.8	230	280	64	0.004	210	55,000
RWE^Y153A	880	46	1.3	370	280	40	0.018	430	25,000

R^V154FWE	310	17	1.6	200	120	12	0.082	130	1,500
RW^V154FE	150	86	0.49	55	110	72	0.018	42	2,400
RWE^V154F	410	5	2.1	230	110	4.2	0.13	180	1,400

R^V154AWE	420	21	1.9	200	100	21	n.d.	n.d.	n.d.
RW^V154AE	390	21	1.5	190	130	20	n.d.	n.d.	n.d.
RWE^V154A	890	5	1.2	170	140	7.7	n.d.	n.d.	n.d.

Values are reported to two significant digits.

ATPase activities of ClpX hexamers in the absence of substrate and ClpP. Rates have an error of ±5% based on replicate measurements (n = 3).

K_M and V_max values were determined by Michaelis-Menten analyses. Errors are ±10% based on replicate measurements (n = 3).

ATPase activities of ClpX hexamers in the presence of saturating concentrations of protein substrate, ClpP, and ATP. Rates have an error of ±5% based on replicate measurements (n = 3).

ATP molecules hydrolyzed per substrate molecule degraded by ClpXP.