Table 1.

Effects of ClpX mutations on ATP-hydrolysis and ClpP interactions.

	ATP hydrolysis (min^-1 enz^-1)		apparent ClpP affinity (nM)
ClpX variant	basal rate^a	% change with ClpP	ATPase assay	protease assay	peptidase assay
WWW/WWW	113	-49	50	70	170
WWWWWW	107	-47	^/	81	^/

WWWWWW^L	112	-30	^/	2800	^/
WWWWW^LW^L	135	^n.b.	^n.b.	^n.b.
WW^LW/WW^LW	141	^n.b.	^n.b.	^n.b.
WE/WE/WE	118	-38	^/	^/	^/
EW^L/EW^L/EW^L	131	^n.b.	^n.b.	^n.b.
WE^L/WE^L/WE^L	130	^n.b.	^n.b.	^n.b.

WWWWWR	209	-41	40	^/	^/
WWWWRR	363	-44	53	^/	^/
RWW/RWW	260	-53	55	75	^/
WWR/WWR	245	-51	^/	^/	^/
WWWRRR	390	-24	160	^/	^/
WR/WR/WR	135	-36	170	^/	^/
RWWRRW	377	-34	150	^/	^/
WRR/WRR	100	^n.b.	^n.b.
WRRRRR	22	^n.b.	^n.b.

ClpX-ΔN	105	-48	50	^/	^/
ClpX-ΔN ^Δpore-2	550	+5	^‡	^‡	2300
ClpX-ΔN ^R191Q	210	-44	40	^/	^/
ClpX-ΔN ^D194N	170	-12	210	^/	^/
ClpX-ΔN ^I198A	125	-42	82	^/	^/
ClpX-ΔN ^R200Q	317	-20	330	^/	660
ClpX-ΔN ^D201N	710	+3	^‡	^‡	2600

RWE/RWE	380	-63	63	^/	^/
RWE^DN/RWE^DN	697	-29	640	^/	^/
RW^DNE/RW^DNE	1090	-30	1400	^/	2900
R^DNWE/R^DNWE	928	-40	430	^/	^/
R^DNWE^DN/R^DNWE^DN	940	+5	^‡	^/	2900
RW^DNE^DN/RW^DNE^DN	929	+17	^/	^/	2400

values below for binding of ClpX variants to ClpP RA12
WWW/WWW	113	-30	^/	320	930
ClpX-ΔN ^D201N			^/	^‡	1900
RW^DNE/RW^DNE			^/	^/	2400
WWWWWW^L			^/	9500	^/

ATPase rates were determined in the absence of ClpP and protein substrate, unlike the values reported by Martin et al. (2005)

value not determined

^n.b.

no binding detected in pull-down assays or in ATPase or protease assays

^‡

assay precluded because mutant ClpXP complex did not degrade GFP-ssrA or showed a small change in ATPase activity

^DN

D201N.

Errors were estimated to be ±5% for ATPase rates and ±20% for apparent affinities based upon replicate measurements for WWW/WWW (± stdev for n ≥ 3). All ClpX variants in this table lack the N-terminal domain.