Abstract
Adenoviruses are large (~950 Å) and complex non-enveloped, dsDNA icosahedral viruses. They have a pseudo-T = 25 triangulation number with at least 12 different proteins composing the virion. These include the major and minor capsid proteins, core proteins, maturation protease, terminal protein, and packaging machinery. Although adenoviruses have been studied for more than 60 years, deciphering their architecture has presented a challenge for structural biology techniques. An outstanding event was the first near-atomic resolution structure of human adenovirus type 5 (HAdV-C5), solved by cryo-electron microscopy (cryo-EM) in 2010. Discovery of new adenovirus types, together with methodological advances in structural biology techniques, in particular cryo-EM, has lately produced a considerable amount of new, high-resolution data on the organization of adenoviruses belonging to different species. In spite of these advances, the organization of the non-icosahedral core is still a great unknown. Nevertheless, alternative techniques such as atomic force microscopy (AFM) are providing interesting glimpses on the role of the core proteins in genome condensation and virion stability. Here we summarize the current knowledge on adenovirus structure, with an emphasis on high-resolution structures obtained since 2010.
Highlights
Adenoviruses soon became an object of interest for structural biologists—they were among the first viruses to be imaged by electron microscopy (EM); their major coat protein was one of the first animal virus proteins to be crystallized; and they were used to demonstrate the possibility of imaging frozen-hydrated biological material in the electron microscope, in the early days of cryoEM
The human adenovirus type 5 (HAdV-C5) virion was the largest biological object ever solved at high resolution by any structural biology technique
Advances in structural biology methods, availability of novel techniques, and discovery of new viruses have resulted in notable advances in our understanding of the adenovirus particle organization and its variations throughout the different species and genera
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The general capsid organization was soon unveiled, reaching the finest details of adenovirus architecture required many years of studies, and could only be attained when cryo-EM realized its potential to provide near-atomic resolution structural data [7]. The human adenovirus type 5 (HAdV-C5) virion was the largest biological object ever solved at high resolution by any structural biology technique. We summarize the knowledge available after publication of the first high-resolution map [7], and discuss new adenovirus-related structures reported since 2010. These include fiber heads and complete virions from previously uncharacterized species and genera, providing new insights into the structural diversity and receptor binding modes within the Adenoviridae family (Table 1).
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