Table 4.

Effect of rpoB2063 and rpoC2064 mutations on the readthrough of the rho-independent transcriptional terminator, T_rplS, of the trmD operon^a

Genotype	Readthrough	Relative readthroughb	Genotype	Readthrough		Mean fold repression ± SDc
				–Ara	+Ara
rpoB+rpoC+	0.084	1.0	nusA+rpoB+rpoC+/pJML007 (nusA+)	0.090	0.099	1.00 ± 0.09
				0.090	0.083
rpoB2063	0.13	1.55	rpoB2063/pJML007 (nusA+)	0.19	0.23	0.75 ± 0.08
				0.16	0.24
rpoC2064	0.086	1.02	rpoC2064/pJML007 (nusA+)	0.098	0.083	1.19 ± 0.01
				0.12	0.10
			nusA94/pJML007 (nusA+)	0.21	0.11	1.66 ± 0.24
				0.17	0.12

^aReadthrough was calculated as [(P + T)/P]. The readthrough of the T_rplS terminator was determined by comparing the β-galactosidase activity of P_metY-metY-T_rplS-lacZ (P + T) and P_metY-metY-lacZ (P) fusions. The effect of induced expression of nusA on the readthrough of this terminator was studied by measuring the β-galactosidase activity in strains harboring plasmid pJML007 that carries nusA under the control of the arabinose-inducible P_BAD promoter. Readthrough was determined with (+Ara) or without (−Ara) the addition of 0.02% arabinose. Only relevant genotypes are indicated. For complete genotypes, see Table 1. The P + T strains used were MW288 (rpoB⁺ rpoC⁺), MW286 (rpoB2063), MW289 (rpoC2064), GOB838/pJML007 (rpoB⁺ rpoC⁺ nusA⁺/nusA⁺), MW286/pJML007 (rpoB2063/nusA⁺), MW289/pJML007 (rpoC2064/nusA⁺), and GOB868/pJML007 (nusA94/nusA⁺); the P strains used were GOB906 (rpoB⁺ rpoC⁺), GOB904 (rpoB2063), GOB908 (rpoC2064), GOB906/pJML007 (rpoB⁺ rpoC⁺ nusA⁺/nusA⁺), GOB904/pJML007 (rpoB2063/nusA⁺), GOB908/pJML007, (rpoC2064/nusA⁺), and GOB752/pJML007 (nusA94/nusA⁺).

^bFor determination of the relative readthrough, the readthrough was normalized to that obtained with nusA⁺ rpoB⁺ rpoC⁺ strains.

^cThe mean fold repression was calculated as the ratio of the readthrough in the absence to that in the presence of arabinose (0.02%).