<p>This entry represents sigma54-dependent transcriptional activators, such as RtcR from <taxon tax_id="562">Escherichia coli</taxon>. RtcR is a transcriptional repressor of rtcBA genes and directly interacts with sigma54 factor [<cite idref="PUB00012945"/>, <cite idref="PUB00042799"/>]. Bacterial transcription relies on the binding of dissociable sigma (sigma) factors to RNA polymerase (RNAP) for promoter specificity. The major variant sigma factor (sigma54) forms a stable closed complex with RNAP bound to DNA that rarely spontaneously isomerises to an open complex [<cite idref="PUB00042800"/>].</p>