Structure and function of lineage-specific sequence insertions in the bacterial RNA polymerase beta' subunit

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Bacterial core RNA polymerase (RNAP) beta and beta' subunits are highly conserved.
• Specific bacterial lineages exhibit large sequence insertions in these subunits.
• The Thermus aquaticus and Escherichia coli RNAP beta' subunits have unique inserts.

Purpose of the Study:

• To investigate the structure of two distinct beta' subunit insertions in bacterial RNAP.
• To elucidate the structural and functional significance of these sequence variations.

Main Methods:

• X-ray crystallography or cryo-electron microscopy for structural determination.
• Sequence analysis to identify conserved motifs and evolutionary relationships.
• Biochemical assays to assess protein-protein and protein-nucleic acid interactions.

Main Results:

• The inserts in both Thermus aquaticus and Escherichia coli beta' subunits are composed of repeating sandwich-barrel hybrid motifs.
• These structural motifs were previously predicted through sequence analysis.
• The inserts play crucial roles in mediating protein/protein and/or protein/nucleic acid interactions.

Conclusions:

• The identified sandwich-barrel hybrid motif is a recurring structural element in bacterial RNAP beta' subunit insertions.
• These insertions are not merely sequence variations but possess functional importance in RNAP interactions.
• Structural insights into these inserts enhance our understanding of bacterial transcription regulation.