Figure 3.

The implications of PS-mediated assembly for the earliest stages of infection. Shown is the asymmetric tomographic structure of MS2, at low resolution, bound to its initial cellular receptor, the E.coli F-pilus. This structure shows extensive density for the viral RNA, confirming the idea that PS-mediated assembly leads to almost identical RNA conformations within each viral particle. The contact to the pilus is mediated by the maturation protein, MP, which also binds to specific sites close to either end of the viral genome. Only the MP-RNA complex enters the bacterial cell, leaving the CP shell largely intact. MP replaces a C/C capsomere in an otherwise icosahedral protein shell.