Table 2.

Fe and S contents and SAM cleavage activities of the PqqE variants

PqqE variant	As‐purified				Reconstituted
	Fe (mol·mol−1)	S (mol·mol−1)	Activity (nmol·min−1·mg−1)	Cluster ratioa	Fe (mol·mol−1)	S (mol·mol−1)	Activity (nmol·min−1·mg−1)	Cluster ratioa
WT	6.35 ± 0.62	10.15 ± 0.65	0.442 ± 0.012	0.89b	11.52 ± 1.05	16.17 ± 1.21	0.858 ± 0.071	1.9
C32S	3.84 ± 0.65b	5.30 ± 0.33b	ndb, c	0.78b	10.50 ± 1.30b	12.10 ± 1.50b	ndc	1.2
C268S	2.12 ± 0.55	3.98 ± 0.93	0.021 ± 0.006	NDc	NDc	NDd	NDd	NDd
C323S	4.12 ± 0.57	7.29 ± 0.72	0.227 ± 0.066	0.37	10.34 ± 1.16	14.18 ± 1.72	0.868 ± 0.109	1.9
C313S	4.21 ± 0.54	7.52 ± 1.18	0.268 ± 0.022	NDc	10.36 ± 0.65	16.17 ± 0.76	0.469 ± 0.019	1.7
C310SC313S	4.09 ± 0.66	6.14 ± 0.81	0.322 ± 0.012	0.21	10.08 ± 1.12	13.58 ± 1.30	0.543 ± 0.042	1.7
C310SC313SC341S	3.72 ± 0.11	7.56 ± 0.42	0.253 ± 0.046	NDc	7.95 ± 0.80	12.01 ± 0.68	0.428 ± 0.108	NDd
D319S	6.15 ± 0.53	9.57 ± 0.78	0.410 ± 0.130	NDc	13.20 ± 1.70	17.89 ± 0.76	0.591 ± 0.031	1.9
C32SC310SC313S	1.69 ± 0.13	2.91 ± 0.17	ndc	0	7.41 ± 0.40	10.56 ± 1.46	ndc	0.9
C28SC32SC310SC313S	1.73 ± 0.17	2.90 ± 0.18	ndc	0	6.03 ± 0.28	9.51 ± 0.35	ndc	1.1
C28SC32SC310SC313SC341S	1.53 ± 0.12	3.10 ± 0.15	ndc	NDc	7.47 ± 0.50	11.34 ± 1.21	ndc	NDd

^aCluster molar ratio ([4Fe–4S]²⁺/[2Fe–2S]²⁺) was calculated from the relative area (RA) of Mössbauer signals including the RA of signals assigned to an Fe atom of [4Fe–4S]²⁺ cluster interacting with the side‐chain carboxyl group of Asp319 at the Aux II site (except for Aux II mutants: C313S, C310SC313S, and D319S).

^bData adopted from the previous study 8.

^cNot detected.

^dNot determined.