Fig 2.

Density sections from the tail regions in the fiberless ϕ29 full (A–C) and empty (D–F) particles. Features with highest or lowest densities appear darkest and lightest, respectively. (A) Longitudinal section of the virion reconstruction labeled to highlight the locations of some phage components. (B,C) Density sections normal to the tail axis at the locations depicted by dashed lines in (A) intersect two portions of the top of the gp10 connector in (B) and the middle of the gp11 lower collar in (C). (D–F) Same as (A–C) for the empty particle. The predominant density features, seen in the virion but not in the empty particle reconstructions, are identified as belonging to DNA and gp3. These include i) the ring of ~190Å diameter that encircles the gp10 dodecamer inside the capsid (B), ii) linear columns positioned along the phage axis and traversing the connector (A,B) and upper tail tube (A), iii) the ~60Å diameter toroid in the connector-collar cavity (A,C), and iv) more diffuse density in the lower portion of the tail tube, terminating at the entrance to the tail knob cavity (A). The twelve asymmetrically arranged copies of gp10 are labeled in (E) but not (B). Scale bar in (F) applies to all panels.