DksA2, a zinc-independent structural analog of the transcription factor DksA

► Structure of the zinc-free DksA2 is similar to that of its zinc-finger paralog DksA. ► DksA2 binds in the RNA polymerase secondary channel. ► A disulfide bond formed by two DksA2 cysteines plays a minor role in DksA2 activity. ► Substitutions of the two cysteine residues destabilize DksA2 structure.