. 2001 Feb;183(3):1022–1031. doi: 10.1128/JB.183.3.1022-1031.2001

TABLE 2.

Cooperative interaction between KorB and TrbA proteins on trbBp-xylE fusion present in plasmid pGBT63^a

Repressor^c	XylE assays of log cultures (0.05 mM IPTG)				XylE assyas of overnight cultures (0.03 mM IPTG)^b				XylE assays of log cultures (0.03 mM IPTG)^b				mRNA analysis of log cultures (0.03 mM IPTG)^b
Repressor^c	XylE units	R_A+B^d	R_A × R_B^e	CI^f	XylE units	R_A+B^d	R_A × R_B^e	CI^f	XylE units	R_A+B^d	R_A × R_B^e	CI^f	mRNA signal^g	R_A+B^d	R_A × R_B^e	CI^f
TrbA + KorB	0.0057 ± 0.0007	203.5	19.1	10.7	0.0047 ± 0.001	1593.6	257	6.19	0.029 ± 0.011	47.2	2.9	16.3	27,861 ± 5,094	61.8	19.8	3.1
KorB	0.14 ± 0.032	8.3			0.32 ± 0.09	23.4			0.61 ± 0.10	2.2			174,792 ± 21,006	9.9
TrbA	0.51 ± 0.13	2.3			0.68 ± 0.012	11			1.03 ± 0.05	1.3			879,996 ± 18,714	2.0
None	1.06 ± 0.28				7.49 ± 1				1.37 ± 0.08				1,722,559 ± 173,010

Each result comes from at least 3 repetitions.

0.03 mM IPTG was used since at 0.05 mM the activity of trbBp was repressed so much as to be unmeasurable.

TrbA was expressed by pMZT24 (tacp-trbA), while KorB was expressed by pDM1.21 (tacp-korB). The equivalent expression vector without repressor gene for each plasmid was pGBT30 and pDM1.2.

Experimentally established repression in the presence of both TrbA and KorB.

Product of indices of repression by TrbA and KorB illustrates the expected repression after introduction of the two repressors together to the same cell if there is no interaction between them.

The ratio of R_A+B/R_A × R_B illustrates the fold enhancement of the repression that the two repressors can mediate when they act together.

Hybridization signal intensity (± standard deviation) of xylE probe hybridized to total RNA.