Modularity of Zorya defense systems during phage inhibition

Area of Science:

• Microbiology
• Structural Biology
• Bacteriophage Research

Background:

• Bacteria possess diverse defense mechanisms against bacteriophages (phages).
• The molecular underpinnings of many anti-phage systems are not fully understood.
• Zorya systems represent a class of bacterial anti-phage defenses.

Purpose of the Study:

• To elucidate the mechanistic and structural basis of Zorya phage defense systems.
• To characterize the core components ZorA and ZorB.
• To identify the effector module of the Zorya II system.

Main Methods:

• Cryo-electron microscopy (cryo-EM) for structural analysis.
• Mutagenesis studies to assess functional importance.
• Biochemical assays to determine effector activity.

Main Results:

• The Zorya type I and II core components, ZorA and ZorB, form a 5:2 complex resembling rotary motors.
• This ZorAB complex features an elongated cytoplasmic tail crucial for function.
• Peptidoglycan binding, cytoplasmic tail structure, and ion flow are vital for system activity.
• ZorE was identified as the nickase effector module of the Zorya II system.

Conclusions:

• The study reveals the molecular architecture and function of Zorya phage defense systems.
• The ZorAB complex acts as an ion-driven motor essential for anti-phage activity.
• ZorE nickase activity is critical for establishing population-wide immunity in the Zorya II system.