biorxiv.org
Sequential assembly in vivo of the bacteriophage P22 genome translocation channel
Bacteriophage P22 ejects four internal proteins into infected cells to assemble a channel for genome translocation across the cell envelope. However, how these proteins cooperate to build the trans-envelope channel remains enigmatic. Using in situ single-particle cryogenic electron microscopy, we determined near-atomic in vivo structures of P22 infection intermediates, revealing how the tail hub protein gp10 templates the sequential assembly of three internal proteins gp7*, gp20 and gp16 into a ~50-nm trans-envelope channel that extends from the virion into the host cytoplasm. Functional analyses explain why phage DNA can be detected in supernatant fluids during infection by channel-defective mutants. Our structures also provide a mechanistic basis for the long-standing observation that a P22 virion lacking gp16 can be complemented, extra-cytoplasmically, by a co-infecting virion lacking gp20, thereby allowing the genome in the gp16-deficient particle to enter the host cytoplasm.
### Competing Interest Statement
The authors have declared no competing interest.
National Institutes of Health, R01 GM124378 (IJM, JL)
National Institutes of Health, R01 GM110243 (JL, IJM)
National Institutes of Health, R01 GM150905 (MC)
