TABLE 2.

Effects of characteristic deletions in the NarX, NarQ, and NarX-CpxA-1 HAMP linkers

Deletionb	β-Galactosidase sp act for sensor kinasea:
	NarX		NarQ		NarX-CpxA-1
	− NO3−	+ NO3−	− NO3−	+ NO3−	− NO3−	+ NO3−
WT	10	1,990	320	1,800	3,550	350
ΔAS-1.1-7	1,550	1,300	90	600	50	40
ΔAS-1.5-11	1,660	1,550	1,980	1,140	NDc	ND
ΔAS-1.8-con2	1,800	1,420	2,740	1,950	30	30
ΔAS-2.1-7	1,330	210	20	20	270	550
ΔAS-2.4-10	510	50	430	20	760	950

^aβ-Galactosidase specific activity was measured as described in Materials and Methods and is expressed in Miller units. Mutant narX and narQ alleles were expressed from derivatives of plasmid pHG165 transformed into strain VJS5054 Φ(narG-lacZ) narX narPQ pcnB. Mutant narX-cpxA-1 alleles were expressed from derivatives of plasmid pHG165 transformed into strain VJS7220 Φ(cpxP-lacZ) cpxA. Cultures were grown anaerobically in the absence or presence of 40 mM NaNO₃.

^bDeletion names indicate the positions in the HAMP linker which have been deleted; see Fig. 1 for graphic representation. WT, wild type.

^cND, not determined.