Fig. 6.

Roles of the ω subunit and ppGpp in p7-mediated antitermination. (A) Termination at the λ tR2 terminator at different p7 concentrations by reconstituted ω-less X. oryzae RNAP without ([ω-], triangles) or with addition of purified ω subunit ([ω-]+ω, squares), either in the absence (open symbols) or in the presence (filled symbols) of NusA. (B) Bacterial two-hybrid analysis of p7 interactions. P7 was fused to the α subunit of E. coli RNAP (interacting with a promoter, P, placed before the reporter lacZ gene) whereas the other interacting partner (x) was fused to the λ CI repressor (interacting with its operator sequence, O). Relative β-galactosidase activities for various p7 partners (in comparison with control noninteracting protein pairs) are shown in the table. (C) Effect of ppGpp on intrinsic termination and p7-dependent antitermination at the λ tR2 terminator. The experiment was performed at 30 °C with native wild-type X. oryzae RNAP in the absence (open symbols) or in the presence (filled symbols) of 100 µM ppGpp.