ATP and other nucleotides stabilize the Rho-mRNA complex

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Transcription termination factor Rho is a hexameric protein crucial for bacterial gene regulation.
• Understanding Rho's assembly on RNA is key to elucidating its mechanism of action.

Purpose of the Study:

• To investigate how Rho protein subunits assemble into active hexamers on RNA.
• To determine the role of nucleotides in Rho-RNA complex formation and its association states.

Main Methods:

• Sedimentation analysis to determine Rho protein association states.
• RNA binding assays measuring complex formation dependence on Rho concentration and nucleotide presence.

Main Results:

• Adenine nucleotides shift RNA binding from a multimeric to a monomeric process.
• Nucleotides stabilize Rho multimers, correlating with altered binding properties.
• Rho hexamer formation on RNA involves subunit addition to partial assemblies, existing in equilibrium with nonhexameric forms.

Conclusions:

• Rho hexamer assembly on RNA is facilitated by adenine nucleotides.
• The findings support models where Rho hexamers form by sequential subunit addition around an RNA transcript.
• This mechanism is critical for Rho-dependent transcription termination in Escherichia coli.