Structure and molecular assignment of lactococcal phage TP901-1 baseplate

Area of Science:

• Bacteriophage biology
• Structural biology
• Microbial genetics

Background:

• Bacteriophages employ baseplates (BP) with receptor-binding proteins (RBPs) to infect bacteria like Lactococcus lactis.
• Understanding BP structure is key to deciphering phage-host interactions.

Purpose of the Study:

• To determine the electron microscopic structure of the TP901-1 phage wild-type and mutant baseplates (BP).
• To elucidate the organization and RBP stoichiometry of the TP901-1 BP for host recognition.

Main Methods:

• Electron microscopy was used to visualize the wild-type and mutant TP901-1 baseplates (BP).
• Electron microscopic reconstruction and light-scattering measurements were employed to analyze BP structure and composition.

Main Results:

• The TP901-1 BP structure reveals a complex organization with peripheral tripods and a central tube.
• A total of 54 receptor-binding proteins (RBPs) were identified, suggesting high avidity for host anchoring.
• The TP901-1 BP exists in an infection-ready conformation, unlike the phage p2 BP.

Conclusions:

• The TP901-1 baseplate (BP) possesses a unique, highly multivalent structure for efficient host cell attachment.
• Comparative analysis of Siphoviridae BPs reveals conserved cores but diverse peripheral structures for varied host recognition strategies.