Adenovirus (AdV) capsid organization is considerably complex, not only
because of its large size (~950 Å) and triangulation number (pseudo T =
25), but also because it contains four types of minor proteins in
specialized locations modulating the quasi-equivalent icosahedral
interactions. Up until 2009, only its major components (hexon, penton,
and fiber) had separately been described in atomic detail. Their
relationships within the virion, and the location of minor coat
proteins, were inferred from combining the known crystal structures with
increasingly more detailed cryo-electron microscopy (cryoEM) maps.
There was no structural information on assembly intermediates. Later on
that year, two reports described the structural differences between the
mature and immature adenoviral particle, starting to shed light on the
different stages of viral assembly, and giving further insights into the
roles of core and minor coat proteins during morphogenesis.
Finally, in 2010, two papers describing the atomic resolution structure
of the complete virion appeared. These reports represent a
veritable tour de force for two structural biology techniques: X-ray
crystallography and cryoEM, as this is the largest macromolecular
complex solved at high resolution by either of them. In particular, the
cryoEM analysis provided an unprecedented clear picture of the complex
protein networks shaping the icosahedral shell. Here I review these
latest developments in the field of AdV structural studies.