Crystal structure of the RNA-binding domain from transcription termination factor rho

Transcription termination factor rho is an ATP-dependent hexameric helicase found in most eubacterial species. The Escherichia coli rho monomer consists of two domains, an RNA-binding domain (residues 1-130) and an ATPase domain (residues 131-419). The ATPase domain is homologous to the beta subunit of F1-ATPase. Here, we report that the crystal structure of the RNA-binding domain of rho (rho130) at 1.55 Angstrom confirms that rho130 contains the oligosaccharide/oligonucleotide-binding (OB) fold, a five stranded beta-barrel. The beta-barrel of rho130 is also surprisingly similiar to the N-terminal beta-barrel of F1 ATPase, extending the applicability of F1 ATPase as a structural model for hexameric rho.