The T7 ejection nanomachine components gp15-gp16 form a spiral ring complex that binds DNA and a lipid membrane.

Bacteriophage T7 initiates infection by ejecting several internal capsid proteins into the host cell; these proteins then assemble into a nanomachine that translocates the viral genome from the phage head into the cytoplasm. The ejected proteins are thought to partially unfold as they pass through the lumen of the portal and the short stubby T7 tail during their entry into the cell. In vivo, the internal proteins gp15 and gp16 assemble into a tubular structure that spans the periplasm and cytoplasmic membrane.