TABLE 3.

Multiple lesions in combination with a cyaY mutation reduce Nuo activity^a

Strain	Relevant genotype	Nuo activityb	Relative activityc
DM8000	Wild type	23,508 ± 136	1.00
DM7220	iscS	3,990 ± 397	0.17
DM7644	cyaY	11,420 ± 518	0.48
DM7642	apbC cyaY	13,631 ± 810	0.58
DM7643	cyaY yggX	17,790 ± 513	0.76
DM5986	yggX apbC	6,146 ± 1239	0.26
DM7641	yggX apbC cyaY	3,375 ± 213	0.14

^aStrains were grown in nutrient broth to an optical density at 650 nm of 0.5. Crude cell-free extracts were generated by sonication as has been described previously (35). The activity of the iscS strain reflects the level of cluster synthesis maintained in a strain lacking the major Fe-S cluster biosynthetic operon. All loci listed for relevant genotypes were inactivated by insertion.

^bNuo activity was measured as described previously, by using d-amino-NADH to distinguish it from the cytoplasmic activity encoded by the ndh gene (39), and is reported as a specific activity (ΔA₆₀₀/min/mg protein [average ± standard deviation]).

^cRelative activity was obtained by dividing the activity of the relevant strain by the activity of the wild-type parent.