Octameric dGTPase assemblies mediate broad anti-phage defense
Deoxyguanosine triphosphatases (dGTPases) are nucleotide-depleting enzymes known to play a role in antiviral defense. While their enzymatic mechanism is established, the structural and functional diversity of dGTPases remains poorly understood. Here, we report a systematic analysis of dGTPase homologs across bacteria, archaea, and eukaryotes, revealing their widespread distribution and association with diverse immune-related domains. Through integrative bioinformatics and structural mining, we identify a class of bacterial dGTPases that assemble into stable octameric and higher-order oligomeric structures. Using cryo-electron microscopy, we resolve the octameric and 16-mer assemblies of a representative Vibrio dGTPase (Vdg) and further captured filamentous forms. Functional assays demonstrate that octamer formation is essential and sufficient for antiviral activity, while higher-order assemblies are dispensable. We also identify dAMP as an allosteric regulator, underscoring the functional versatility of dGTPases. Our findings provide insights into the modular architecture, oligomerization-driven activation, and immune function of bacterial dGTPases, and broaden our understanding of nucleotide depletion-based antiviral strategies. Deoxyguanosine triphosphatases (dGTPases) are nucleotide-depleting enzymes that contribute to antiviral defense. Here, the authors reveal widespread and structurally diverse dGTPases and characterize oligomeric dGTPases in distinct assembly states, providing insights into their architecture, activation, and regulation.