Figure 5.
A UL19 pentamer-like external protrusion is present on the structure yielded by a tomographic averaging experiment in which vertices were selected, one per capsid, on the basis of their having density underlying the floor layer at the vertex site. The reference template (a) was a uniform solid cylinder of 14 nm in height and 10 nm in diameter, mounted with its top flush with the outer surface of the floor layer. In each capsid, it should detect the vertex with the most density in this region, regardless of what density there may be outside the floor. (b) The resulting averaged vertex structure (central section). (c) Corresponding section of a model with the UL6 portal seated in the floor layer and pointing inwards. In panel (b), there is a faint annulus under the bloor (arrow). This density is much weaker than that in the shell, indicating substoichiometric occupancy, and its apparent symmetry (left/right) results from the cylindrical averaging that was performed to boost the signal-to-noise ratio. Bar = 20 nm.