The structural basis for terminator recognition by the Rho transcription termination factor

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The Rho protein is essential for transcription termination in bacteria like E. coli.
• It disengages newly transcribed RNA from the DNA template.
• Understanding Rho's RNA-binding mechanism is key to deciphering transcription regulation.

Purpose of the Study:

• To determine the X-ray crystal structure of the RNA-binding domain of E. coli Rho.
• To elucidate the structural basis for Rho's RNA sequence specificity.
• To propose a model for the allosteric regulation of the Rho hexamer.

Main Methods:

• X-ray crystallography was used to determine the structure of the Rho RNA-binding domain complexed with an RNA ligand.
• Analysis of the crystal structure revealed specific features of the RNA-binding site.
• Computational modeling was employed to develop a model for the intact Rho hexamer.

Main Results:

• The crystal structure identified filters within the RNA-binding site that confer sequence specificity.
• These filters explain Rho's preference for cytosine-rich RNA.
• Crystal packing showed two Rho domain protomers binding a single RNA with a single base spacer, suggesting a mechanism for strong RNA binding.

Conclusions:

• The structure of the Rho RNA-binding domain provides insights into its sequence recognition capabilities.
• The findings suggest that RNA-binding module pairing contributes to Rho's affinity for RNA.
• A model of subunit dimerization on an asymmetric ligand explains allosteric control in the Rho hexamer.