Marta Pérez-Illana Marta Pérez-Illana Anna Schachner Anna Schachner Mercedes Hernando-Pérez Mercedes Hernando-Pérez Gabriela N. Condezo Gabriela N. Condezo Alberto Paradela Alberto Paradela Marta Martínez Marta Martínez Roberto Marabini Roberto Marabini Michael Hess Michael Hess Carmen San Martín Carmen San Martín Public Library of Science 2025 High-resolution structural studies have mainly focused on two out of the six adenovirus genera: mastadenoviruses and atadenoviruses. Here we report the high-resolution structure of an aviadenovirus, the poultry pathogen fowl adenovirus serotype 4 (FAdV-C4). FAdV-C4 virions are highly thermostable, despite lacking minor coat and core proteins shown to stabilize the mast- and atadenovirus particles, having no genus-specific cementing proteins, and packaging a 25% longer genome. Unique structural features of the FAdV-C4 hexon include a large insertion at the trimer equatorial region, and a long N-terminal tail. Protein IIIa conformation is closer to atadenoviruses than to mastadenoviruses, while protein VIII diverges from all previously reported structures. We interpret these differences in light of adenovirus evolution. Finally, we discuss the possible role of core composition in determining capsid stability properties. These results enlarge our view on the structural diversity of adenoviruses, and provide useful information to counteract fowl pathogens or use non-human adenoviruses as vectors. PDFDocument eng 2026-04-28T09:00:58.651751Z 2025 Viral Structure Protein Interactions Monomers Bird Genomics Protein Structure Virions Adenoviruses Viral Packaging 3277753 b application/pdf http://creativecommons.org/licenses/by/4.0/