A single residue determines the cooperative binding property of a primosomal DNA replication protein, PriB, to...

Area of Science:

• Molecular Biology
• Bacterial DNA Replication
• Protein-DNA Interactions

Background:

• PriB is a crucial primosomal protein essential for bacterial DNA replication re-initiation.
• Understanding PriB's DNA-binding properties is key to elucidating replication mechanisms.

Purpose of the Study:

• To characterize and compare the single-stranded DNA (ssDNA)-binding properties of PriB from Salmonella Typhimurium (StPriB) and Escherichia coli (EcPriB).
• To investigate the impact of a single amino acid difference (V6 in EcPriB vs. A6 in StPriB) on DNA binding.
• To propose models for stable PriB-ssDNA complex formation.

Main Methods:

• Comparative biochemical characterization of StPriB and EcPriB DNA-binding.
• Analysis of structural information regarding residue V6/A6 at the dimer-dimer interface.
• Development of binding models for PriB-ssDNA complexes.

Main Results:

• StPriB and EcPriB exhibit significantly different cooperative binding mechanisms to ssDNA.
• EcPriB forms a single complex with ssDNA, whereas StPriB forms two or more distinct complexes.
• The single amino acid difference at position 6 does not directly impede ssDNA binding but influences complex formation.

Conclusions:

• The distinct ssDNA binding modes of StPriB and EcPriB highlight functional divergence despite high sequence similarity.
• These findings provide insights into the structural basis for differential PriB complex formation with ssDNA.
• Proposed binding models offer a framework for understanding stable PriB-ssDNA interactions in bacterial replication.