An extended RNA binding surface through arrayed S1 and KH domains in transcription factor NusA

Area of Science:

• Structural biology
• Molecular biology
• Biochemistry

Background:

• NusA is a transcription factor crucial for regulating bacterial gene expression.
• It plays key roles in transcription pausing, termination, and antitermination.
• Understanding NusA structure is vital for elucidating its regulatory mechanisms.

Purpose of the Study:

• To determine the crystal structure of Thermotoga maritima NusA.
• To investigate the structural basis for mRNA binding and recognition.
• To understand how NusA domains cooperate in RNA interaction.

Main Methods:

• X-ray crystallography was used to determine the high-resolution crystal structure of T. maritima NusA.
• Homology modeling was employed to predict interactions with specific mRNA sequences.
• Structural and mutational analyses were performed to assess domain cooperation and RNA binding.

Main Results:

• The structure reveals a four-domain, rod-shaped molecule with an N-terminal alpha/beta portion, an S1 domain (beta-barrel), and two K-homology (KH) domains.
• A continuous spine of positive electrostatic potential facilitates nonspecific mRNA attraction.
• The S1 and KH motifs are positioned to recognize specific mRNA regulatory sequences, forming an extended RNA binding surface.

Conclusions:

• The conserved arrangement of S1 and KH domains in NusA provides a paradigm for other proteins with similar domain arrays.
• Cooperative interactions between these motifs modulate both the strength and specificity of RNA binding.
• The findings provide structural insights into NusA's role in transcription regulation.