. 2000 Mar 7;97(6):2656–2661. doi: 10.1073/pnas.050578997

Table 2.

Effect of deletion of the terminator in the yczA-ycbK leader region on trp operon expression

Genetic background	Construct label	β-Galactosidase activity, Miller units^*
Genetic background	Construct label	− Trp	+ Trp
mtrB⁺yczA⁺ycbK⁺		13	0.1
mtrB264 yczA⁺ycbK⁺		215	187
mtrB⁺ ΔTerminator yczA⁺ycbK′^†	ΔTerm-592	50	40
mtrB264 ΔTerminator yczA⁺ ycbK′^†	ΔTerm-592	213	193
mtrB⁺ ΔTerminator Δ(′yczA⁺-ycbK′)^‡	ΔTerm-365	16	<0.1
mtrB⁺ ΔTerminator Δ(′yczA⁺-ycbK′)^§	ΔTerm-416	22	<0.1
mtrB⁺ ΔTerminator yczA⁺ ΔycbK′^¶	ΔTerm-525	24	18

Strains were grown in minimal medium with or without 50 μg/ml tryptophan at 37°C. All terminator-deletion fragments were integrated into the remnant of the ycbK locus in the chromosome as described in Materials and Methods.

Strains contain a trpE′-′lacZ translational fusion integrated in the amyE locus. Each assay was performed in duplicate on at least four separate occasions.

^† Fragment (712 bp) ending at nucleotide 592 containing a deletion of the leader region terminator integrated into the chromosome. ΔTerm-592 (see Fig. 1).

^‡ Fragment (485 bp) ending at nucleotide 365 containing a deletion of the leader region terminator. ΔTerm-365.

^§ Fragment (536 bp) ending at nucleotide 416 containing a deletion of the leader region terminator. ΔTerm-416.

^¶ Fragment (645 bp) ending at nucleotide 525 containing a deletion of the leader region terminator. ΔTerm-525.