To infect an Escherichia coli bacterium, a λ virus must get its DNA through the cell’s outer membrane, through the mesh of cross-linked polymers that forms the cell wall, and then through the cell’s inner membrane. How the viruses’ progeny escape through those same three layers is the focus of a new paper by Ry Young of Texas A&M University and his collaborators. Previous research had elucidated two of the steps—opening a hole in the inner membrane and dissolving the polymer mesh. It had also implicated a pair of viral proteins, Rz and Rz1, in breaching the outer membrane. The longer molecule, Rz, binds to the inner membrane and has the potential to fold over onto itself; Rz1 binds to the outer membrane. Before the polymer mesh is dissolved, Rz and Rz1 bond to form spanin, a molecular complex that threads through the mesh to span the inner and outer...

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