LAUSR

The HelD is a helicase‐like protein binding to Bacillus subtilis RNA polymerase (RNAP), stimulating transcription in an ATP‐dependent manner. Here, our small angle X‐ray scattering data bring the first insights into the HelD structure: HelD is compact in shape and undergoes a conformational change upon substrate analog binding. Furthermore, the HelD domain structure is delineated, and a partial model of HelD is presented. In addition, the unique N‐terminal domain of HelD is characterized as essential for its transcription‐related function but not for ATPase activity, DNA binding, or binding to RNAP. The study provides a topological basis for further studies of the role of HelD in transcription.