Mycobacteriophage structure reveals the molecular architecture for its host interaction and viral genome ejection
Recent reports highlight the efficacy of engineered mycobacteriophages to treat non-tuberculosis mycobacterial disease. Molecular-level insights into mycobacteriophage architecture and host interactions could allow structure-guided phage engineering to increase efficacy and broaden host range, but such information is currently unavailable. We describe the cryo-EM structure of mycobacteriophage Douge at resolutions ranging from 2.18 to 4.0 Å. Our atomic model reveals that the assembly of this 400 nm-long, pin-shaped phage, containing 1105 protein subunits assembled into a complete siphophage, coated with 919 glycan-binding domains for mycobacterial cell surface interactions. Our structure also suggests a unique way of the tape measurement protein (TMP) for DNA gating mechanism. When filled with viral genome, the channel spann ing the connector, tail, and baseplate is sealed by tape measure proteins, providing a genome gating system, and requiring limited structural changes for genome ejection upon phage–host contact. Nanometer-resolution cryo-ET snapshots of phage–host interactions show that the baseplate remains attached to the mycobacterial outer membrane during viral genome ejection. This study reveals high-resolution structural details of this mycobacteriophage and its interaction with host glycans.