Table 1. Biochemical data for base variants with individual ATPase mutations.

Summary of ATP hydrolysis rates (base), peptidase stimulation (CP and base), and degradation rates (reconstituted 26S proteasomes) for all base variants included in this study. Values for each assay are expressed both in absolute terms and as a normalized percentage of wild-type base activity. Base mutants are designated as EQ (Walker-B), YA (pore-1 loop), DN (pore-2 loop), NT (C-terminal tail truncation), and KS (Walker-A), followed by a number indicating which Rpt subunit contained the mutation (1–6). Degradation activities for WT base and EQ mutants are included for both multiple turnover (left) and single turnover (right) conditions. Errors were estimated to be ±10% (s.d.) based on repeat measurements (n ≥ 3 technical replicates).

	Residue Mutated	basal ATPase rate		peptidase stimulation		degradation rate (kdeg)
		min−1	% WT	fold increase	% WT	(enz−1 min−1)	% WT
Holoenzyme	-	107	-	-	-	0.32	-
WT (E. coli)	-	51	100	21	100	0.30	100
WT (yeast)	-	54	106	22	103	0.29	97
EQ hexamer	-	2	4	24	110	0.00	0.00
EQ1	310	35	68	15	68	0.08 / 0.12	27 / 40
EQ2	284	82	161	29	134	0.28 / 0.24	92 / 79
EQ3	273	17	33	19	89	0.005 / 0.00	2 / 0
EQ4	282	55	108	20	95	0.001 / 0.00	0.41 / 0
EQ5	282	34	67	25	118	0.13 / 0.21	44 / 72
EQ6	249	83	164	35	161	0.02 / 0.01	6 / 5
YA1	284	66	129	18	84	0.30	101
YA2	257	75	148	8	38	0.15	52
YA3	246	44	87	17	81	0.19	62
YA4	255	38	75	14	65	0.16	54
YA5	255	89	174	15	68	0.22	74
YA6	222	38	76	18	82	0.26	87
DN1	327	39	76	23	106	0.21	71
EN2	300	59	115	24	110	0.27	91
DN3	289	65	127	20	91	0.16	52
DN4	298	141	278	41	192	0.22	74
DN5	298	90	177	32	149	0.40	134
DN6	265	58	113	18	84	0.29	96
NT1	464–468	61	121	20	91	0.29	98
NT2	434–438	45	88	2	10	0.13	44
NT3	424–428	65	127	1	5	0.05	16
NT4	433–437	49	97	23	108	0.25	83
NT5	430–434	86	169	1	7	0.14	47
NT6	401–405	53	104	5	24	0.25	83
KS1	257	32*	62*	15	71	0.07*	24*
KS2	230	13*	25*	2	10	nd*	nd*
KS3	219	29*	57*	12	58	0.08*	26*
KS4	228	15*	29*	15	68	0.001*	0.40*
KS5	228	74*	147*	13	59	0.02*	6*
KS6	195	22*	43*	12	54	0.04*	15*

nd = not determined

^*ATPase and degradation activities for the WA-KS mutants represent lower bounds due to varying degrees of misassembly observed for these base mutants.