Conformational flexibility of σ70 in anti‐terminator loading

In promoter DNA, the preferred distance of the ?10 and ?35 elements for interacting with RNA polymerase‐bound σ⁷⁰ is 17 bp. However, the Devi et al. paper in this issue of Molecular Microbiology demonstrates that when the C‐terminal domain of σ⁷⁰, including the 3.2 linker, is not attached to the core enzyme, distances between 0 and 3 bp can be accommodated. This attests to the great flexibility of the 3.2 linker. The particularly stable complex with the 2 bp separation may lend itself to structural studies of an early elongation complex containing σ⁷⁰.