Table 1.

In vivo antitermination at different Rho-dependent terminators by various N and RNAP alleles

Source of N	N alleles	RNAP alleles	Plac-nutR/tR1-lacZYAa			Plac-nutR/tR1-trpt'-lacZYAb
			β−galactosidase activities (A.U.)			β−galactosidase activities (A.U.)
			+ter	−ter	%RT	+ter	−ter	%RT
H-19B	WT	WT	998 ± 25	2916 ± 89	34.2	927 ± 67	2916 ± 89	31.8
	R3H		335 ± 17	4196 ± 554	7.9
	S11F		223 ± 16	4404 ± 565	5.1
	R15C		136 ± 12	3374 ± 331	4.0
	R15P		142 ± 9	3844 ± 335	3.7
	R18P		157 ± 4	3545 ± 709	4.4	3.9 ± 1.2	2201 ± 150	0.18
	Δ78-127		293 ± 45	3574 ± 488	8.2
	Δ88-127		445 ± 21	3611 ± 590	12.3
	Δ96-127		489 ± 11	2745 ± 372	17.8	38 ± 2	2745 ± 372	1.4
	Δ101-127		730 ± 14	2485 ± 152	29.4	243 ± 16	2485 ± 153	9.8
	Δ106-127		670 ± 21	3006 ± 116	22.3	368 ± 25	3006 ± 116	12.2
	Δ111-127		648 ± 17	2851 ± 112	22.7	166 ± 8	2851 ± 112	5.8
	Δ121-127		769 ± 11	2912 ± 130	26.4	707 ± 36	2912 ± 130	24.3
λc	WT	WT	1026 ± 70	2699 ± 196	38.0
	Δ73-107		192 ± 13	2642 ± 175	7.3
	Δ81-107		860 ± 65	2450 ± 292	35.1
	Δ91-107		940 ± 64	2613 ± 210	36.0
	Δ101-107		989 ± 50	2488 ± 139	39.8
H-19Bd	WT	WT	980 ± 25	1969 ± 82	49.7	834 ± 31	2049 ± 90	40.7
		P251S, P254L	460 ± 41	1327 ± 45	34.7	303 ± 24	1565 ± 102	19.3
		R270C	883 ± 33	2934 ± 342	30.1	636 ± 35	2573 ± 262	24.7

The above strains were transformed with the plasmids bearing different WT and mutant H-19B N (or λ N) genes. The ratio of β-galactosidase values in the presence (+ter) and absence (−ter) of terminator gives the efficiency of terminator read-through (%RT). Two terminator-lacZYA fusions, t_R1-lacZYA and t_R1-trpt'-lacZYA, were used. The Rho-dependent terminator, t_R1 was derived from the nutR-cro region of either a lambdoid phage H-19B (for H-19B N) or the λphage (for λ N). The errors are calculated from the average of 4 to 5 independent measurements.

^aStrains RS734 (+ter) and RS445(−ter)

^bStrains RS1017(+ter) and RS445(−ter)

^cStrains RS1019 and RS445 with nutR/tR1 of λ-phage

^dStrains RS941(+ter) and RS940(−ter); ^eStrains RS1029 (+ter) and RS940 (−ter); Experiments were performed at 42°C to inactivate the temperature sensitive (ts) allele of WT rpoC present in the chromosome and the WT and mutant rpoC were supplied from the plasmids. Anti-termination efficiency increases at higher temperature. These two rpoC mutants did not support H-19B N mediated anti-termination and also the growths of λ and H-19B phages (16). These mutants are located near the RNA exit channel of the EC.