Figure 3.

Binding of the 70–184, 70–215, 70–268, and 70–324 peptides to core RNA polymerase. A constant amount of core (E) was combined with increasing amounts of σ peptides (S′). Formation of a holoenzyme (H′) was detected as the presence of a faster migrating species when compared with E alone (lanes 1 and 6). All σ peptides formed a holoenzyme complex at a ratio of 1:1 with E (lanes 3, 8, 12, and 16). Other ratios E/S′) were 1:4 (lanes 4, 9, 13, and 17) and 1:10 (lanes 5, 10, 14, and 18). Free σ peptides (lanes 2, 7, 11, and 15) are also shown. In a separate experiment (data not shown), on native gels the order of mobility for the free σ peptides was 70–324 = 70–184 < 70–268 < 70–215.