Antiterminator LoaP loads onto RNA to chase a runaway RNA polymerase.

In this issue of Structure, Elghondakly et al. 1 present the crystal structure of Thermoanaerobacter pseudethanolicus antiterminator LoaP, a member of a ubiquitous family of NusG transcription factors, bound to its target, a dfn RNA hairpin. LoaP uses RNA as a recognition determinant, which is unique among NusG paralogs and makes unusual contacts in the major groove of the RNA.