E. coli 6S RNA release from RNA polymerase requires σ⁷⁰ ejection by scrunching and is orchestrated by a conserved RNA hairpin

A 6S:pRNA:Eσ⁷⁰ intermediate state (S3) revealed by nucleotide feeding experiments. (A) Native gel analysis of ³²P body-labeled 6S RNA (6S*) showing the emergence and decline of the S3 state when pRNA synthesis is initiated with AU dinucleotide (GTP concentration 25.9 μM, ATP withheld). Time points are 0.25, 0.5, 1, 2, 4, 8, 16, and 32 min. F indicates free 6S* (S1); B, bound Eσ⁷⁰ complex (S2). (B) Fitted data for the S2 and S3 state kinetics shown in panel A (for fitting details, see Materials and Methods) using Supplemental Equations 4 and 5, respectively.