Functional carbohydrate binding modules identified in evolved dits from siphophages infecting various Gram-positive...

Area of Science:

• Microbiology
• Structural Biology
• Bioinformatics

Background:

• Bacteriophages are viruses that infect bacteria.
• Siphophages, a type of bacteriophage, possess tail structures involved in host attachment.
• Recent studies have identified novel decorations in the tail and neck structures of 936 group lactococcal siphophages.

Purpose of the Study:

• To identify and characterize carbohydrate-binding modules (CBMs) in bacteriophage Dits.
• To investigate the structural conservation and functional role of these CBMs in phage-host adhesion.
• To explore the prevalence of evolved Dits in phages infecting Gram-positive bacteria.

Main Methods:

• Bioinformatic analysis to identify conserved CBMs in Dit proteins.
• Structural analysis to classify CBM folds into distinct groups.
• Heterologous expression of CBM-GFP fusions for binding assays.
• Confocal microscopy to visualize and confirm host binding.

Main Results:

• A conserved CBM was identified in many virion baseplate Dit components, distinct from classical receptor-binding proteins (RBPs).
• Evolved Dit proteins contain structurally conserved CBMs that fall into four distinct classes.
• Fluorescent binding assays confirmed the specific host-binding capabilities of these CBMs.
• Evolved Dits were detected in phages infecting various Gram-positive bacteria, including mycobacteria.

Conclusions:

• Carbohydrate-binding modules (CBMs) are prevalent in siphophages, suggesting an auxiliary role in infection.
• These CBMs facilitate specific host recognition and attachment, enhancing phage-host adhesion.
• The findings contribute to understanding the structural assembly and functionality of phage adhesion devices.