Mapping the ligand-binding region of Borrelia burgdorferi fibronectin-binding protein BBK32

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Pathogenic microorganisms utilize microbial adhesins to bind fibronectin, facilitating cellular attachment and entry.
• A previously identified Borrelia burgdorferi gene, bbk32, encodes a 47-kDa fibronectin-binding protein.

Purpose of the Study:

• To localize the ligand-binding region of the Borrelia burgdorferi BBK32 fibronectin-binding protein.
• To investigate the sequence diversity and functional conservation of the bbk32 gene across different B. burgdorferi isolates.
• To explore potential shared mechanisms of cellular adhesion between B. burgdorferi and Streptococcus pyogenes.

Main Methods:

• Localization of the BBK32 ligand-binding region using biochemical assays.
• Cloning and sequencing of the bbk32 gene from multiple B. burgdorferi isolates.
• Expression of BBK32 proteins in Escherichia coli to assess fibronectin-binding activity.
• Bioinformatic analysis to compare amino acid sequences and identify homologies.

Main Results:

• The ligand-binding region of BBK32 was localized to a 32-amino acid domain.
• All sequenced bbk32 genes from different B. burgdorferi isolates encoded functional fibronectin-binding proteins.
• The ligand-binding domain showed 81-91% amino acid sequence identity among the isolates.
• Sequence homology was identified between the BBK32 ligand-binding region and a fibronectin-binding peptide of Streptococcus pyogenes protein F1.

Conclusions:

• The BBK32 protein from Borrelia burgdorferi possesses a conserved fibronectin-binding region crucial for pathogen adhesion.
• Structural and functional similarities suggest a common mechanism for cellular adhesion and entry involving fibronectin binding for both B. burgdorferi and Streptococcus pyogenes.